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Publisher: John Wiley and Sons   (Total: 1579 journals)

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Showing 1 - 200 of 1579 Journals sorted alphabetically
Abacus     Hybrid Journal   (Followers: 13, SJR: 0.48, h-index: 22)
About Campus     Hybrid Journal   (Followers: 5)
Academic Emergency Medicine     Hybrid Journal   (Followers: 65, SJR: 1.385, h-index: 91)
Accounting & Finance     Hybrid Journal   (Followers: 47, SJR: 0.547, h-index: 30)
ACEP NOW     Free   (Followers: 1)
Acta Anaesthesiologica Scandinavica     Hybrid Journal   (Followers: 52, SJR: 1.02, h-index: 88)
Acta Archaeologica     Hybrid Journal   (Followers: 156, SJR: 0.101, h-index: 9)
Acta Geologica Sinica (English Edition)     Hybrid Journal   (Followers: 3, SJR: 0.552, h-index: 41)
Acta Neurologica Scandinavica     Hybrid Journal   (Followers: 5, SJR: 1.203, h-index: 74)
Acta Obstetricia et Gynecologica Scandinavica     Hybrid Journal   (Followers: 15, SJR: 1.197, h-index: 81)
Acta Ophthalmologica     Hybrid Journal   (Followers: 6, SJR: 0.112, h-index: 1)
Acta Paediatrica     Hybrid Journal   (Followers: 56, SJR: 0.794, h-index: 88)
Acta Physiologica     Hybrid Journal   (Followers: 6, SJR: 1.69, h-index: 88)
Acta Polymerica     Hybrid Journal   (Followers: 9)
Acta Psychiatrica Scandinavica     Hybrid Journal   (Followers: 35, SJR: 2.518, h-index: 113)
Acta Zoologica     Hybrid Journal   (Followers: 6, SJR: 0.459, h-index: 29)
Acute Medicine & Surgery     Hybrid Journal   (Followers: 4)
Addiction     Hybrid Journal   (Followers: 35, SJR: 2.086, h-index: 143)
Addiction Biology     Hybrid Journal   (Followers: 13, SJR: 2.091, h-index: 57)
Adultspan J.     Hybrid Journal   (SJR: 0.127, h-index: 4)
Advanced Energy Materials     Hybrid Journal   (Followers: 27, SJR: 6.411, h-index: 86)
Advanced Engineering Materials     Hybrid Journal   (Followers: 26, SJR: 0.81, h-index: 81)
Advanced Functional Materials     Hybrid Journal   (Followers: 51, SJR: 5.21, h-index: 203)
Advanced Healthcare Materials     Hybrid Journal   (Followers: 14, SJR: 0.232, h-index: 7)
Advanced Materials     Hybrid Journal   (Followers: 265, SJR: 9.021, h-index: 345)
Advanced Materials Interfaces     Hybrid Journal   (Followers: 6, SJR: 1.177, h-index: 10)
Advanced Optical Materials     Hybrid Journal   (Followers: 6, SJR: 2.488, h-index: 21)
Advanced Science     Open Access   (Followers: 5)
Advanced Synthesis & Catalysis     Hybrid Journal   (Followers: 17, SJR: 2.729, h-index: 121)
Advances in Polymer Technology     Hybrid Journal   (Followers: 13, SJR: 0.344, h-index: 31)
Africa Confidential     Hybrid Journal   (Followers: 21)
Africa Research Bulletin: Economic, Financial and Technical Series     Hybrid Journal   (Followers: 13)
Africa Research Bulletin: Political, Social and Cultural Series     Hybrid Journal   (Followers: 10)
African Development Review     Hybrid Journal   (Followers: 33, SJR: 0.275, h-index: 17)
African J. of Ecology     Hybrid Journal   (Followers: 15, SJR: 0.477, h-index: 39)
Aggressive Behavior     Hybrid Journal   (Followers: 15, SJR: 1.391, h-index: 66)
Aging Cell     Open Access   (Followers: 11, SJR: 4.374, h-index: 95)
Agribusiness : an Intl. J.     Hybrid Journal   (Followers: 6, SJR: 0.627, h-index: 14)
Agricultural and Forest Entomology     Hybrid Journal   (Followers: 16, SJR: 0.925, h-index: 43)
Agricultural Economics     Hybrid Journal   (Followers: 45, SJR: 1.099, h-index: 51)
AIChE J.     Hybrid Journal   (Followers: 31, SJR: 1.122, h-index: 120)
Alcoholism and Drug Abuse Weekly     Hybrid Journal   (Followers: 7)
Alcoholism Clinical and Experimental Research     Hybrid Journal   (Followers: 7, SJR: 1.416, h-index: 125)
Alimentary Pharmacology & Therapeutics     Hybrid Journal   (Followers: 33, SJR: 2.833, h-index: 138)
Alimentary Pharmacology & Therapeutics Symposium Series     Hybrid Journal   (Followers: 3)
Allergy     Hybrid Journal   (Followers: 51, SJR: 3.048, h-index: 129)
Alternatives to the High Cost of Litigation     Hybrid Journal   (Followers: 3)
American Anthropologist     Hybrid Journal   (Followers: 143, SJR: 0.951, h-index: 61)
American Business Law J.     Hybrid Journal   (Followers: 24, SJR: 0.205, h-index: 17)
American Ethnologist     Hybrid Journal   (Followers: 90, SJR: 2.325, h-index: 51)
American J. of Economics and Sociology     Hybrid Journal   (Followers: 28, SJR: 0.211, h-index: 26)
American J. of Hematology     Hybrid Journal   (Followers: 33, SJR: 1.761, h-index: 77)
American J. of Human Biology     Hybrid Journal   (Followers: 12, SJR: 1.018, h-index: 58)
American J. of Industrial Medicine     Hybrid Journal   (Followers: 16, SJR: 0.993, h-index: 85)
American J. of Medical Genetics Part A     Hybrid Journal   (Followers: 16, SJR: 1.115, h-index: 61)
American J. of Medical Genetics Part B: Neuropsychiatric Genetics     Hybrid Journal   (Followers: 4, SJR: 1.771, h-index: 107)
American J. of Medical Genetics Part C: Seminars in Medical Genetics     Partially Free   (Followers: 6, SJR: 2.315, h-index: 79)
American J. of Physical Anthropology     Hybrid Journal   (Followers: 37, SJR: 1.41, h-index: 88)
American J. of Political Science     Hybrid Journal   (Followers: 269, SJR: 5.101, h-index: 114)
American J. of Primatology     Hybrid Journal   (Followers: 15, SJR: 1.197, h-index: 63)
American J. of Reproductive Immunology     Hybrid Journal   (Followers: 3, SJR: 1.347, h-index: 75)
American J. of Transplantation     Hybrid Journal   (Followers: 17, SJR: 2.792, h-index: 140)
American J. on Addictions     Hybrid Journal   (Followers: 9, SJR: 0.843, h-index: 57)
Anaesthesia     Hybrid Journal   (Followers: 134, SJR: 1.404, h-index: 88)
Analyses of Social Issues and Public Policy     Hybrid Journal   (Followers: 10, SJR: 0.397, h-index: 18)
Analytic Philosophy     Hybrid Journal   (Followers: 18)
Anatomia, Histologia, Embryologia: J. of Veterinary Medicine Series C     Hybrid Journal   (Followers: 3, SJR: 0.295, h-index: 27)
Anatomical Sciences Education     Hybrid Journal   (Followers: 1, SJR: 0.633, h-index: 24)
Andrologia     Hybrid Journal   (Followers: 2, SJR: 0.528, h-index: 45)
Andrology     Hybrid Journal   (Followers: 2, SJR: 0.979, h-index: 14)
Angewandte Chemie     Hybrid Journal   (Followers: 193)
Angewandte Chemie Intl. Edition     Hybrid Journal   (Followers: 218, SJR: 6.229, h-index: 397)
Animal Conservation     Hybrid Journal   (Followers: 39, SJR: 1.576, h-index: 62)
Animal Genetics     Hybrid Journal   (Followers: 8, SJR: 0.957, h-index: 67)
Animal Science J.     Hybrid Journal   (Followers: 6, SJR: 0.569, h-index: 24)
Annalen der Physik     Hybrid Journal   (Followers: 5, SJR: 1.46, h-index: 40)
Annals of Anthropological Practice     Partially Free   (Followers: 2, SJR: 0.187, h-index: 5)
Annals of Applied Biology     Hybrid Journal   (Followers: 7, SJR: 0.816, h-index: 56)
Annals of Clinical and Translational Neurology     Open Access   (Followers: 1)
Annals of Human Genetics     Hybrid Journal   (Followers: 9, SJR: 1.191, h-index: 67)
Annals of Neurology     Hybrid Journal   (Followers: 47, SJR: 5.584, h-index: 241)
Annals of Noninvasive Electrocardiology     Hybrid Journal   (Followers: 2, SJR: 0.531, h-index: 38)
Annals of Public and Cooperative Economics     Hybrid Journal   (Followers: 9, SJR: 0.336, h-index: 23)
Annals of the New York Academy of Sciences     Hybrid Journal   (Followers: 5, SJR: 2.389, h-index: 189)
Annual Bulletin of Historical Literature     Hybrid Journal   (Followers: 13)
Annual Review of Information Science and Technology     Hybrid Journal   (Followers: 14)
Anthropology & Education Quarterly     Hybrid Journal   (Followers: 25, SJR: 0.72, h-index: 31)
Anthropology & Humanism     Hybrid Journal   (Followers: 17, SJR: 0.137, h-index: 3)
Anthropology News     Hybrid Journal   (Followers: 15)
Anthropology of Consciousness     Hybrid Journal   (Followers: 11, SJR: 0.172, h-index: 5)
Anthropology of Work Review     Hybrid Journal   (Followers: 11, SJR: 0.256, h-index: 5)
Anthropology Today     Hybrid Journal   (Followers: 91, SJR: 0.545, h-index: 15)
Antipode     Hybrid Journal   (Followers: 48, SJR: 2.212, h-index: 69)
Anz J. of Surgery     Hybrid Journal   (Followers: 7, SJR: 0.432, h-index: 59)
Anzeiger für Schädlingskunde     Hybrid Journal   (Followers: 1)
Apmis     Hybrid Journal   (Followers: 1, SJR: 0.855, h-index: 73)
Applied Cognitive Psychology     Hybrid Journal   (Followers: 70, SJR: 0.754, h-index: 69)
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 7, SJR: 0.632, h-index: 58)
Applied Psychology     Hybrid Journal   (Followers: 198, SJR: 1.023, h-index: 64)
Applied Psychology: Health and Well-Being     Hybrid Journal   (Followers: 49, SJR: 0.868, h-index: 13)
Applied Stochastic Models in Business and Industry     Hybrid Journal   (Followers: 5, SJR: 0.613, h-index: 24)
Aquaculture Nutrition     Hybrid Journal   (Followers: 14, SJR: 1.025, h-index: 55)
Aquaculture Research     Hybrid Journal   (Followers: 31, SJR: 0.807, h-index: 60)
Aquatic Conservation Marine and Freshwater Ecosystems     Hybrid Journal   (Followers: 36, SJR: 1.047, h-index: 57)
Arabian Archaeology and Epigraphy     Hybrid Journal   (Followers: 11, SJR: 0.453, h-index: 11)
Archaeological Prospection     Hybrid Journal   (Followers: 12, SJR: 0.922, h-index: 21)
Archaeology in Oceania     Hybrid Journal   (Followers: 13, SJR: 0.745, h-index: 18)
Archaeometry     Hybrid Journal   (Followers: 27, SJR: 0.809, h-index: 48)
Archeological Papers of The American Anthropological Association     Hybrid Journal   (Followers: 15, SJR: 0.156, h-index: 2)
Architectural Design     Hybrid Journal   (Followers: 25, SJR: 0.261, h-index: 9)
Archiv der Pharmazie     Hybrid Journal   (Followers: 4, SJR: 0.628, h-index: 43)
Archives of Drug Information     Hybrid Journal   (Followers: 5)
Archives of Insect Biochemistry and Physiology     Hybrid Journal   (SJR: 0.768, h-index: 54)
Area     Hybrid Journal   (Followers: 12, SJR: 0.938, h-index: 57)
Art History     Hybrid Journal   (Followers: 243, SJR: 0.153, h-index: 13)
Arthritis & Rheumatology     Hybrid Journal   (Followers: 50, SJR: 1.984, h-index: 20)
Arthritis Care & Research     Hybrid Journal   (Followers: 26, SJR: 2.256, h-index: 114)
Artificial Organs     Hybrid Journal   (Followers: 1, SJR: 0.872, h-index: 60)
ASHE Higher Education Reports     Hybrid Journal   (Followers: 14)
Asia & the Pacific Policy Studies     Open Access   (Followers: 16)
Asia Pacific J. of Human Resources     Hybrid Journal   (Followers: 321, SJR: 0.494, h-index: 19)
Asia Pacific Viewpoint     Hybrid Journal   (Followers: 1, SJR: 0.616, h-index: 26)
Asia-Pacific J. of Chemical Engineering     Hybrid Journal   (Followers: 8, SJR: 0.345, h-index: 20)
Asia-pacific J. of Clinical Oncology     Hybrid Journal   (Followers: 6, SJR: 0.554, h-index: 14)
Asia-Pacific J. of Financial Studies     Hybrid Journal   (SJR: 0.241, h-index: 7)
Asia-Pacific Psychiatry     Hybrid Journal   (Followers: 4, SJR: 0.377, h-index: 7)
Asian Economic J.     Hybrid Journal   (Followers: 8, SJR: 0.234, h-index: 21)
Asian Economic Policy Review     Hybrid Journal   (Followers: 4, SJR: 0.196, h-index: 12)
Asian J. of Control     Hybrid Journal   (SJR: 0.862, h-index: 34)
Asian J. of Endoscopic Surgery     Hybrid Journal   (SJR: 0.394, h-index: 7)
Asian J. of Organic Chemistry     Hybrid Journal   (Followers: 5, SJR: 1.443, h-index: 19)
Asian J. of Social Psychology     Hybrid Journal   (Followers: 5, SJR: 0.665, h-index: 37)
Asian Politics and Policy     Hybrid Journal   (Followers: 12, SJR: 0.207, h-index: 7)
Asian Social Work and Policy Review     Hybrid Journal   (Followers: 5, SJR: 0.318, h-index: 5)
Asian-pacific Economic Literature     Hybrid Journal   (Followers: 5, SJR: 0.168, h-index: 15)
Assessment Update     Hybrid Journal   (Followers: 4)
Astronomische Nachrichten     Hybrid Journal   (Followers: 2, SJR: 0.701, h-index: 40)
Atmospheric Science Letters     Open Access   (Followers: 29, SJR: 1.332, h-index: 27)
Austral Ecology     Hybrid Journal   (Followers: 15, SJR: 1.095, h-index: 66)
Austral Entomology     Hybrid Journal   (Followers: 9, SJR: 0.524, h-index: 28)
Australasian J. of Dermatology     Hybrid Journal   (Followers: 8, SJR: 0.714, h-index: 40)
Australasian J. On Ageing     Hybrid Journal   (Followers: 6, SJR: 0.39, h-index: 22)
Australian & New Zealand J. of Statistics     Hybrid Journal   (Followers: 14, SJR: 0.275, h-index: 28)
Australian Accounting Review     Hybrid Journal   (Followers: 4, SJR: 0.709, h-index: 14)
Australian and New Zealand J. of Family Therapy (ANZJFT)     Hybrid Journal   (Followers: 3, SJR: 0.382, h-index: 12)
Australian and New Zealand J. of Obstetrics and Gynaecology     Hybrid Journal   (Followers: 47, SJR: 0.814, h-index: 49)
Australian and New Zealand J. of Public Health     Hybrid Journal   (Followers: 11, SJR: 0.82, h-index: 62)
Australian Dental J.     Hybrid Journal   (Followers: 7, SJR: 0.482, h-index: 46)
Australian Economic History Review     Hybrid Journal   (Followers: 4, SJR: 0.171, h-index: 12)
Australian Economic Papers     Hybrid Journal   (Followers: 29, SJR: 0.23, h-index: 9)
Australian Economic Review     Hybrid Journal   (Followers: 6, SJR: 0.357, h-index: 21)
Australian Endodontic J.     Hybrid Journal   (Followers: 3, SJR: 0.513, h-index: 24)
Australian J. of Agricultural and Resource Economics     Hybrid Journal   (Followers: 3, SJR: 0.765, h-index: 36)
Australian J. of Grape and Wine Research     Hybrid Journal   (Followers: 5, SJR: 0.879, h-index: 56)
Australian J. of Politics & History     Hybrid Journal   (Followers: 14, SJR: 0.203, h-index: 14)
Australian J. of Psychology     Hybrid Journal   (Followers: 18, SJR: 0.384, h-index: 30)
Australian J. of Public Administration     Hybrid Journal   (Followers: 406, SJR: 0.418, h-index: 29)
Australian J. of Rural Health     Hybrid Journal   (Followers: 5, SJR: 0.43, h-index: 34)
Australian Occupational Therapy J.     Hybrid Journal   (Followers: 72, SJR: 0.59, h-index: 29)
Australian Psychologist     Hybrid Journal   (Followers: 12, SJR: 0.331, h-index: 31)
Australian Veterinary J.     Hybrid Journal   (Followers: 20, SJR: 0.459, h-index: 45)
Autism Research     Hybrid Journal   (Followers: 34, SJR: 2.126, h-index: 39)
Autonomic & Autacoid Pharmacology     Hybrid Journal   (SJR: 0.371, h-index: 29)
Banks in Insurance Report     Hybrid Journal   (Followers: 1)
Basic & Clinical Pharmacology & Toxicology     Hybrid Journal   (Followers: 11, SJR: 0.539, h-index: 70)
Basic and Applied Pathology     Open Access   (Followers: 2, SJR: 0.113, h-index: 4)
Basin Research     Hybrid Journal   (Followers: 5, SJR: 1.54, h-index: 60)
Bauphysik     Hybrid Journal   (Followers: 2, SJR: 0.194, h-index: 5)
Bauregelliste A, Bauregelliste B Und Liste C     Hybrid Journal  
Bautechnik     Hybrid Journal   (Followers: 1, SJR: 0.321, h-index: 11)
Behavioral Interventions     Hybrid Journal   (Followers: 9, SJR: 0.297, h-index: 23)
Behavioral Sciences & the Law     Hybrid Journal   (Followers: 24, SJR: 0.736, h-index: 57)
Berichte Zur Wissenschaftsgeschichte     Hybrid Journal   (Followers: 9, SJR: 0.11, h-index: 5)
Beton- und Stahlbetonbau     Hybrid Journal   (Followers: 2, SJR: 0.493, h-index: 14)
Biochemistry and Molecular Biology Education     Hybrid Journal   (Followers: 6, SJR: 0.311, h-index: 26)
Bioelectromagnetics     Hybrid Journal   (Followers: 1, SJR: 0.568, h-index: 64)
Bioengineering & Translational Medicine     Open Access  
BioEssays     Hybrid Journal   (Followers: 10, SJR: 3.104, h-index: 155)
Bioethics     Hybrid Journal   (Followers: 14, SJR: 0.686, h-index: 39)
Biofuels, Bioproducts and Biorefining     Hybrid Journal   (Followers: 1, SJR: 1.725, h-index: 56)
Biological J. of the Linnean Society     Hybrid Journal   (Followers: 16, SJR: 1.172, h-index: 90)
Biological Reviews     Hybrid Journal   (Followers: 4, SJR: 6.469, h-index: 114)
Biologie in Unserer Zeit (Biuz)     Hybrid Journal   (Followers: 42, SJR: 0.12, h-index: 1)
Biology of the Cell     Full-text available via subscription   (Followers: 9, SJR: 1.812, h-index: 69)
Biomedical Chromatography     Hybrid Journal   (Followers: 6, SJR: 0.572, h-index: 49)
Biometrical J.     Hybrid Journal   (Followers: 5, SJR: 0.784, h-index: 44)
Biometrics     Hybrid Journal   (Followers: 36, SJR: 1.906, h-index: 96)
Biopharmaceutics and Drug Disposition     Hybrid Journal   (Followers: 10, SJR: 0.715, h-index: 44)
Biopolymers     Hybrid Journal   (Followers: 18, SJR: 1.199, h-index: 104)
Biotechnology and Applied Biochemistry     Hybrid Journal   (Followers: 45, SJR: 0.415, h-index: 55)
Biotechnology and Bioengineering     Hybrid Journal   (Followers: 160, SJR: 1.633, h-index: 146)
Biotechnology J.     Hybrid Journal   (Followers: 14, SJR: 1.185, h-index: 51)
Biotechnology Progress     Hybrid Journal   (Followers: 39, SJR: 0.736, h-index: 101)
Biotropica     Hybrid Journal   (Followers: 20, SJR: 1.374, h-index: 71)
Bipolar Disorders     Hybrid Journal   (Followers: 9, SJR: 2.592, h-index: 100)
Birth     Hybrid Journal   (Followers: 38, SJR: 0.763, h-index: 64)
Birth Defects Research Part A : Clinical and Molecular Teratology     Hybrid Journal   (Followers: 2, SJR: 0.727, h-index: 77)
Birth Defects Research Part B: Developmental and Reproductive Toxicology     Hybrid Journal   (Followers: 6, SJR: 0.468, h-index: 47)
Birth Defects Research Part C : Embryo Today : Reviews     Hybrid Journal   (SJR: 1.513, h-index: 55)
BJOG : An Intl. J. of Obstetrics and Gynaecology     Partially Free   (Followers: 241, SJR: 2.083, h-index: 125)

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Journal Cover Advanced Engineering Materials
  [SJR: 0.81]   [H-I: 81]   [26 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1438-1656 - ISSN (Online) 1527-2648
   Published by John Wiley and Sons Homepage  [1579 journals]
  • Microstructure and Texture Development in Al–3%Brass Composite
           Produced through ARB
    • Authors: Ehsan Tolouei; Mohammad Reza Toroghinejad, Hamed Asgari, Hossein Monajati Zadeh, Fakhreddin Ashrafizadeh, Jerzy A. Szpunar, Philippe Bocher
      Abstract: In the present work, aluminum-3% brass composite sheets are produced by accumulative roll bonding (ARB) process up to nine passes at ambient temperature. Evolution of rolling texture is studied by texture measurement using X-ray diffraction method. The results show that ARB process leads to the formation of copper ({112} ) and Dillamore ({4 4 11} ) as the major texture components. The intensity of copper and Dillamore components enhances to values as high as 19 times that of random with increasing number of passes to 9. It is observed that the 5th pass is a transition in development of the texture components, after which the intensities undergo a drop. The textures are comparable to ARB process of high purity aluminum, indicating that the addition of 3% brass particles do not cause any significant change in the deformation behavior. Electron backscatter diffraction (EBSD) technique is used to examine the microstructure; the results reveal formation of ultrafine grains (UFG), starting in the 3rd pass and covers the entire structure after the 5th pass. The major mechanisms involved are identified as rotation of the sub-grains, as well as grain boundary migration.Aluminum–brass composite is produced by ARB process up to nine passes. Recrystallization and formation of new grains start from the 3rd pass and continues to the 7th pass. Intensity of the textures decreases after recrystallization; Dillamore and Copper components are the main textures of the composite.
      PubDate: 2017-11-17T02:31:33.642186-05:
      DOI: 10.1002/adem.201700463
       
  • An Evaporative Initiated Chemical Vapor Deposition Coater for Nanoglue
           Bonding
    • Authors: Greg C. Randall; Luis Gonzalez, Ron Petzoldt, Fred Elsner
      Abstract: The authors present an evaporative initiated chemical vapor deposition (iCVD) coater and use it to establish a submicron bonding process for millimeter-scale foils with potentially rough surface features. The coater uses a simple benchtop design suited to research labs, with pre-heated metal pins instead of hot filaments, and direct evaporation of reactants within the chamber. Coatings of poly(glycidyl methacrylate) (pGMA) with thickness 100–800 nm are achieved at rates of 10–40 nm min−1 on substrates common in high energy laser compression experiments. Coating uniformities of 10–30 nm mm−1 are demonstrated in a ≈60 × 10 mm zone under the heated pins. As an aside, the authors further show the ability to coat intentionally non-uniform layers in a monomer vapor diffusion gradient. Coatings are formed on both plastics and solids ranging from smooth, non-burred silicon or lithium fluoride to rough and burred metals (aluminum and copper). These coated substrates are then chemically bonded under mild heat and pressure. Detailed surface, thickness, and cross-sectional characterization is performed to confirm a submicron bond gap and to troubleshoot the common clearance issues from burrs, roughness, and surface curvature. Peeling and dropping bond strength tests confirm the bonds are robust, when coated and assembled under conditions to mitigate clearance issues.A simplified evaporative initiated chemical vapor deposition (iCVD) coater is developed for submicron bond gaps in materials with potentially imperfect surfaces. A robust bonding process is designed to overcome the most common irregular surface features (curvature, roughness, and burrs) followed from contact elasticity analysis. Bond gaps of 0.2–1.5 µm are achieved in combinations of common plastics, metals, and ceramic-like foils.
      PubDate: 2017-11-16T10:00:30.304446-05:
      DOI: 10.1002/adem.201700839
       
  • Nanometer-Thick Ionic Liquids as Boundary Lubricants
    • Authors: Xiao Gong; Lei Li
      Abstract: Ionic liquids (ILs) are fascinating materials with unique combination of solid and liquid properties. Due to high thermal stability and promising tribological properties, there have been increasing research interests in applying ILs as boundary lubricants. In this review, the authors will discuss the recent progress on this topic with the emphasis on the relationship between the molecular arrangement of ILs confined to a solid and the tribological properties. First, the fundamentals on boundary lubrication and the state-of-the-art lubricants will be reviewed briefly. Second, the progress on the molecular structure of ILs confined to a solid surface will be discussed. Afterward, the experimental and computational efforts on the ILs as boundary lubricants will be discussed in details with emphasis on the effect of IL structure, solid substrates, and IL-soild interaction. Finally, the future research directions will be discussed.Ionic liquids (ILs) are fascinating materials with unique combination of solid and liquid properties. In this review, we discuss the recent progress on their potential application as boundary lubricants with the emphasis on the relationship between the molecular arrangement of ILs confined to a solid and the tribological properties.
      PubDate: 2017-11-15T11:58:30.954432-05:
      DOI: 10.1002/adem.201700617
       
  • Diversity in Addressing Reaction Mechanisms of Nano-Thermite Composites
           with a Layer by Layer Structure
    • Authors: Hongtao Sui; Lauren LeSergent, John Z. Wen
      Abstract: The reaction mechanisms and microstructures of various layered nano-thermite composites are investigated through characterization of their energetic properties. Migration of reactive components across the reaction zone is analyzed, which plays an important role in determining the process initiation, reaction propagation, and chemical stability at low temperatures. Distinct types of nanoparticles are deposited onto filter paper in a sequence, using the vacuum filtration method, which promotes intimate contact between neighboring reactive layers. Scanning Electron Microscopy (SEM) images demonstrate a well-defined contact region between the two layers in the Al/CuO or Al/NiO composites. Differential Scanning Calorimetry (DSC) data shows that the thermite reaction occurs below the melting temperature of Al, resulting in rapid heat release, and improves reaction initiation. Elemental mapping results reveal the migration of Al, Ni/Cu, and oxygen before and after the thermite reaction, which is arranged during thermogravimetric analysis (TGA). This analysis indicates the dominant pathway of the thermite reaction in each composite, through either decomposition of the CuO nanoparticles in the Al/CuO composite or through direct migration of reactive components across the conducting surface within the Al/NiO composite.Layer-by-layer structured Al–CuO and Al–NiO nanoparticles are investigated via characterization of their microstructures and elemental mapping. Experimental data indicates for Al–CuO the reaction involves decomposition of CuO into oxygen, while for Al–NiO migration of reactive species across the conducting surface is critical.
      PubDate: 2017-11-15T11:57:02.787975-05:
      DOI: 10.1002/adem.201700822
       
  • 3D Printing of Diamond Tools for Dental Ceramics Processing
    • Authors: Zhibo Yang; Junchen Hu, Kaiqiang Li, Aiju Liu, Shian Liu
      Abstract: This paper is focused on preparing diamond tools with orderly arranged abrasive particles for dental ceramics processing via 3D printing. This allows one to overcome such drawbacks of the existing methods of dental ceramics processing as weak bonding strength, short service life, and irregular diamond distribution in diamond tools. Firstly, the CAD model of the dental diamond tool is constructed using 3D cartographic software, with level-scan-path geometry information generated via hierarchcal slicing. Then, using Ni–Cr alloy powder and diamond as raw materials, the dental ceramics processing diamond tool with orderly arranged diamond particles is prepared via a 3D printer. Next, an X-ray diffractometer, energy dispersive spectrometer, and scanning electron microscope are used to analyze the microstructure of the Ni–Cr alloy and diamond particle interfaces, resulting in the identification of their bonding mechanism. Finally, the diamond grinding wheel produced by 3D printing is subjected to dental zirconia ceramics grinding performance tests. The results obtained confirm that diamond particles experience normal wear, while no abrasive falling off occurs on the 3D printed diamond tool surface.In this paper, diamond tools for dental ceramics processing are manufactured using the 3D printing technology. Laser fast scanning is utilized to make the 3D distribution of diamond particles more regular, thus, significantly improving the manufacturing performance of grinding wheels.
      PubDate: 2017-11-15T11:56:27.324339-05:
      DOI: 10.1002/adem.201700747
       
  • Smart Energetics: Sensitization of the Aluminum-Fluoropolymer Reactive
           System
    • Authors: Sara L. Row; Lori J. Groven
      Abstract: The development of smart energetics is at the forefront of the research community. The desire is to have energetics that could have ON/OFF capability, tunable performance, and/or targeted energy delivery. Therefore, efforts have been focused on designing systems that respond to stimuli in a controlled manner. In this paper, nanoscale aluminum (nAl)/fluoropolymer reactive systems are studied and the piezoelectric nature of the fluoropolymers is used as a means to sensitize the system. Using a capacitor type setup, and drawing on our previous efforts, three fluoropolymer/nAl systems are studied and their sensitivities upon application of a DC voltage are quantified using BAM drop weight as the indicator. It is found, upon application of 1.0 kV, that for all three fluoropolymer/Al systems the sensitivity is greatly increased. For example, for the THV221/nAl system the impact energy required for ignition is reduced from 63 to 10 J. Further increasing the applied voltage is shown to further increase the sensitivity for all systems studied. The role of electroactive phase content and sensitization time is also discussed.Aluminum/fluoropolymer reactives are formulated and demonstrate switchable behavior upon application of a DC voltage. The drop weight sensitivity is on par with powdered RDX and PETN. This demonstrates that piezoelectric fluoropolymer bound reactives could be developed into smart energetics.
      PubDate: 2017-11-14T12:50:22.264431-05:
      DOI: 10.1002/adem.201700409
       
  • Impact of Cement Hydration on Durability of Cellulosic Fiber-Reinforced
           Cementitious Composites in the Presence of Metakaolin
    • Authors: Jianqiang Wei
      Abstract: Degradation of cellulosic fiber in the alkaline environment of concrete generated in the process of cement hydration is the primary reason for the low durability of such composites. However, the impact of cement hydration on cellulosic fiber's degradation in cementitious systems has not been thoroughly understood. This paper presents the dependence of deterioration behavior of cellulosic fiber-cement systems on cement hydration in the presence of metakaolin. Experimental investigations, such as isothermal calorimetry, thermogravimetric analysis and energy dispersive X-ray spectroscopy, and thermodynamic simulations are carried out to investigate cement hydration kinetics and hydration products. Durability of cellulosic fiber-reinforced cement composite is assessed based on the degradation in flexural properties. The results indicate that, in the presence of metakaolin, the hydration of cement is enhanced accompanied by consumption of calcium hydroxide, low release of hydration heat, decreased Ca/Al and Ca/Si ratios of C–S–H phase, and reduced OH- and Ca2+ amounts in pore solution. A cement substitution by 30 wt% metakaolin results in an improvement of flexural toughness and durability of cellulosic fiber-reinforced cement composites by 42 and 269%, respectively. The correlations between composite durability and hydration of Portland cement are established.Hydration of cement is identified as a crucial factor in understanding the deterioration behavior of cellulosic fibers-reinforced cementitious composites. Effect of metakaolin, on durability of cellulosic fiber-reinforced cement composites are evaluated by means of degradation in flexural properties. Based on the experimental and simulation observations, correlations between durability of cellulosic fiber-cement system and cement chemistry are established.
      PubDate: 2017-11-14T02:27:19.086803-05:
      DOI: 10.1002/adem.201700642
       
  • Production and Anisotropic Tensile Behavior of Resin-Metal
           Interpenetrating Phase Composites
    • Authors: Bibo Yao; Zhaoyao Zhou, Liuyang Duan, Jie Qin
      Abstract: Metal-polymer composites can be used to synthesize material properties. A variety of interpenetrating phase composites have been produced by spontaneously infiltrating porous short-fiber preforms with unsaturated polyester resin under vacuum conditions. Porous preforms are fabricated by compacting and sintering short 304 stainless steel fibers from cutting stainless steel fiber ropes. Tensile experiments are conducted, and fractographs are examined via scanning electron microscopy. The results reveal that the tensile strength, elongation at maximum stress, and elasticity modulus of the IPCs increase with the increasing fiber fractions and exhibit anisotropy in different directions. The tensile strength and elongation at maximum stress are significantly improved compared with the consistent preforms. A nonlinear elastic behavior and sawtooth-like fluctuation during yield deformation are noted. Compared with the through-thickness direction, a higher tensile strength and larger elongation at maximum stress are observed in the in-plane direction. Finer-diameter fibers can improve the strength and increase the elongation at maximum stress. The tensile fracture surfaces show a mixture of brittle and plastic fracture characteristics.Metal-resin IPCs are produced by vacuum-infiltration of unsaturated polyester resin into the stainless steel preforms and their tensile properties are analyzed. The tensile strength and elongation at maximum stress increase with the increasing fiber fractions and exhibit anisotropy. Finer diameter fibers can improve the strength and increase the elongation at maximum stress. The tensile fracture surfaces show a mixture of brittle and plastic fracture characterizations.
      PubDate: 2017-11-14T02:25:36.705722-05:
      DOI: 10.1002/adem.201700669
       
  • Mesoporous Silica Spheres Incorporated Aluminum/Poly (Vinylidene Fluoride)
           for Enhanced Burning Propellants
    • Authors: Haiyang Wang; Jeffery B. DeLisio, Scott Holdren, Tao Wu, Yong Yang, Junkai Hu, Michael R. Zachariah
      Abstract: In this paper, we demonstrate that preparation by electrospray deposition of mesoporous SiO2 particles can be employed as additives to Aluminum/Poly (Vinylidene Fluoride) (Al/PVDF) to enhance reaction velocity. We find that the reaction velocity of Al/PVDF with 5 wt% SiO2 is 3× higher. The presence of meso-SiO2 appears to accelerate the decomposition of PVDF, with a significant increase in HF release, resulting in higher heat release. We believe that hot-spots around meso-SiO2 may serve as multiple ignition points, with the multi-layered structure promoting heat convection to increase the propagation rate.With 5 wt% mesoporous silica, the burning rate of Al/PVDF film was 3× times higher. The meso-SiO2 appears to highly accelerate the decomposition of PVDF, with a significant increase in HF release and higher heat release. Hot-spots around meso-SiO2 may serve as multiple ignition points and the multi-layered structure promote the heat convection thus highly increase the spreading rate.
      PubDate: 2017-11-14T02:25:26.939421-05:
      DOI: 10.1002/adem.201700547
       
  • Microstructure-Dependent Local Fatigue Cracking Resistance of Bimodal
           Ti–6Al–4V Alloys
    • Authors: Ling-Rong Zeng; Li-Ming Lei, Jia Yang, Xue-Mei Luo, Guang-Ping Zhang
      Abstract: The fatigue crack growth behavior of the bimodal Ti–6Al–4V alloys with two different volume fractions of the primary α phase (αp) of 76 and 36% is investigated by the in situ testing technique. The experimental results show that the crack growth rate of the αp = 36% Ti–6Al–4V alloy is lower than that of the αp = 76% one. The local fatigue crack growth rate is evidently decreased by the various boundaries including αp grain boundaries, boundaries between the αp phase and basketweave microstructure, and α/β lamellar interfaces. A criterion associated with the boundary characteristics is obtained to evaluate the grain boundary resistance to the fatigue crack growth in the engineering alloys.Local crack growth rate and fatigue cracking resistance of the Ti–6Al–4V alloys with different volume fractions of primary α phases are investigated in situ in SEM. Local resistance to fatigue cracking related to the boundary characteristics is evaluated quantitatively by EBSD. A criterion for the grain boundary resistance to the crack growth is proposed.
      PubDate: 2017-11-13T03:15:37.565735-05:
      DOI: 10.1002/adem.201700702
       
  • Influence of Ingot and Powder Metallurgy Production Route on the Tensile
           Creep Behavior of Mo–9Si–8B Alloys with Additions of Al and Ge
    • Authors: P. M. Kellner; R. Völkl, U. Glatzel
      Abstract: Refractory metals and their alloys show potential for high temperature applications, due to the elevated melting points often paired with very good creep resistance. Spark plasma sintering (SPS) as well as arc-melting is used here to prepare quaternary and quinternary Mo–9Si–8B–xAl–yGe (x is 0 or 2; y is 0 or 2, all numbers in at%) samples. All samples consist of a Mo solid solution (Moss) and two intermetallic phases: Mo3Si (A15) and Mo5SiB2 (T2). Aluminum and germanium reduce the melting point and slightly decrease the density of the material. The specimens are homogenized and coarsened by a subsequent heat-treatment in vacuum at 1850 °C for 24 h. The resulting microstructure is investigated using scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), and inductively coupled plasma optical emission spectrometry (ICP-OES) analysis. A vacuum creep testing device for small tensile creep specimens is presented. It is heated by graphite radiation heaters usable up to 1500 °C in vacuum of 2 · 10-4 Pa with an oil diffusion pump. Tensile creep tests are performed at 1250 °C and stresses from 50 MPa up to 250 MPa. Specimens produced by ingot metallurgy feature superior creep properties compared to powder metallurgy samples.In this study, tensile creep tests are performed for Mo–Si–B alloys at 1250 °C and stresses from 50 to 250 MPa manufactured by argon arc melting and powder metallurgy. Specimens produced by argon arc melted feature superior creep properties compared to powder metallurgy ones, due to grain size.
      PubDate: 2017-11-13T02:46:55.570691-05:
      DOI: 10.1002/adem.201700751
       
  • Macroporous SiOC Ceramics with Dense Struts by Positive Sponge Replication
           Technique
    • Authors: Abhisek Choudhary; Swadesh K. Pratihar, Ashish K. Agrawal, Shantanu K. Behera
      Abstract: Highly porous SiOC ceramics (≥90% open porosity) containing dense struts have been prepared following positive sponge replication technique using silsesquioxane based preceramic polymer. The morphological features including cell size, cell window size, and strut size of the macroporous SiOC ceramics have been analyzed using electron microscopy. Subtle variation in the crosslinking condition of the preceramic polymer infiltrated polyurethane template enables the formation of hollow as well as dense struts, which has a profound influence on compressive strength of the macroporous bodies. Synchrotron radiation micro computed tomography is used to construct the three dimensional images of the macroporous ceramics that indicate isotropy of the pores and excellent interconnectivity.Control of slurry viscosity and crosslinking temperature in the processing of preceramic polymer infiltrated PU sponge affords macroporous SiOC ceramics with 90% open porosity, dense struts, and excellent mechanical strength. Synchrotron X-ray microtomography exhibits excellent interconnectivity, homogeneity, and isotropy of the pores.
      PubDate: 2017-11-09T12:02:36.46478-05:0
      DOI: 10.1002/adem.201700586
       
  • Key Factors Achieving Large Recovery Strains in Polycrystalline
           Fe–Mn–Si-Based Shape Memory Alloys: A Review
    • Authors: Huabei Peng; Jie Chen, Yongning Wang, Yuhua Wen
      Abstract: Fe–Mn–Si-based shape memory alloys are the most favorable for large-scale applications owing to low cost, good workability, good machinability, and good weldability. However, polycrystalline Fe–Mn–Si-based shape memory alloys have low recovery strains of only 2–3% after solution treatment, although monocrystalline ones reach a large recovery strain of ≈9%. This review gives an overview of the improvement of recovery strains for polycrystalline Fe–Mn–Si-based shape memory alloys. It is proposed that two fundamental aspects, that is, composition design and microstructure design, shall be satisfied for obtaining large recovery strains of above 6%. Alloying compositions determining the ceiling of recovery strains shall follow three guidelines: (i) Si content is 5–6 wt%; (ii) 20 wt% ≤ Mn ≤ 32 wt%; (iii) addition of elements strongly strengthening austenite matrix. Microstructure design includes coarsening austenitic grains and reducing twin boundaries as far as possible together with introducing a high density of stacking faults and second phases of strengthening austenite.Low cost Fe–Mn–Si-based shape memory alloys are suitable for large-scale applications. However, their recovery strains are only 2–3% in solution-treated polycrystalline status. This review summarizes the origin of shape memory effect and the improvement history of recovery strains. It is concluded that two fundamental aspects, that is, composition design and microstructure design, shall be followed to achieve a large recovery strain of above 6%.
      PubDate: 2017-11-09T11:56:27.165908-05:
      DOI: 10.1002/adem.201700741
       
  • Mechanical Properties and Interlaminar Fracture Toughness of
           Glass-Fiber-Reinforced Epoxy Composites Embedded with Shape Memory Alloy
           Wires
    • Authors: Li-Dan Xu; Ming-Fang Shi, Xiao-Yu Sun, Zhen-Qing Wang, Bin Yang
      Abstract: The effects of the content and position of shape memory alloy (SMA) wires on the mechanical properties and interlaminar fracture toughness of glass-fiber-reinforced epoxy (GF/epoxy) composite laminates are investigated. For this purpose, varying numbers of SMA wires are embedded in GF/epoxy composite laminates in different stacking sequences. The specimens are prepared by vacuum-assisted resin infusion (VARI) processing and are subjected to static tensile and three-point-bending tests. The results show that specimens with two SMA wires in the stacking sequence of [GF2/SMA/GF1/SMA/GF2] and four SMA wires in the stacking sequence of [GF4/SMA/GF2/SMA/GF4] exhibit optimal performance. The flexural strength of the optimal four-SMA-wire composite is lower than that of the pure GF/epoxy composite by 5.76% on average, and the flexural modulus is improved by 5.19%. Mode-I and II interlaminar fracture toughness tests using the SMA/GF/epoxy composite laminates in the stacking sequence of [GF4/SMA/GF2/SMA/GF4] are conducted to evaluate the mechanism responsible for decreasing the mechanical properties. Scanning electron microscopy (SEM) observations reveal that the main damage modes are matrix delamination, interfacial debonding, and fiber pullout.The effects of the content and position of shape memory alloy (SMA) wires on the mechanical properties and interlaminar fracture toughness of glass-fiber-reinforced epoxy (GF/epoxy) composite laminates are investigated. The main damage modes are studied by Scanning electron microscopy (SEM).
      PubDate: 2017-11-09T11:55:52.804025-05:
      DOI: 10.1002/adem.201700646
       
  • Stress Reduction of 3D Printed Compliance-Tailored Multilayers
    • Authors: Shanmugam Kumar; Brian L. Wardle, Muhamad F. Arif, Jabir Ubaid
      Abstract: Multilayered multi-material interfaces are encountered in an array of fields. Here, enhanced mechanical performance of such multi-material interfaces is demonstrated, focusing on strength and stiffness, by employing bondlayers with spatially-tuned elastic properties realized via 3D printing. Compliance of the bondlayer is varied along the bondlength with increased compliance at the ends to relieve stress concentrations. Experimental testing to failure of a tri-layered assembly in a single-lap joint configuration, including optical strain mapping, reveals that the stress and strain redistribution of the compliance-tailored bondlayer increases strength by 100% and toughness by 60%, compared to a constant modulus bondlayer, while maintaining the stiffness of the joint with the homogeneous stiff bondlayer. Analyses show that the stress concentrations for both peel and shear stress in the bondlayer have a global minimum when the compliant bond at the lap end comprises ≈10% of the bondlength, and further that increased multilayer performance also holds for long (relative to critical shear transfer length) bondlengths. Damage and failure resistance of multi-material interfaces can be improved substantially via the compliance-tailoring demonstrated here, with immediate relevance in additive manufacturing joining applications, and shows promise for generalized joining applications including adhesive bonding.By crafting a spatially compliance-tailored bondlayer utilizing additive manufacturing, mechanical performance can be increased significantly compared to the homogeneous stiff or compliant bondlayer, imparting greater strength, strain to break, and toughness, while maintaining stiffness of the homogeneous stiff bondlayer.
      PubDate: 2017-11-08T08:15:47.562197-05:
      DOI: 10.1002/adem.201700883
       
  • Effect of Laser Shock Peening on the Microstructures and Properties of
           Oxide-Dispersion-Strengthened Austenitic Steels
    • Authors: Xueliang Yan; Fei Wang, Leimin Deng, Chenfei Zhang, Yongfeng Lu, Michael Nastasi, Marquis A. Kirk, Meimei Li, Bai Cui
      Abstract: Oxide-dispersion-strengthened (ODS) austenitic steels are promising materials for next-generation fossil and nuclear energy systems. In this study, laser shock peening (LSP) has been applied to ODS 304 austenitic steels, during which a high density of dislocations, stacking faults, and deformation twins are generated in the near surface of the material due to the interaction of laser-driven shock waves and the austenitic steel matrix. The dispersion particles impede the propagation of dislocations. The compressive residual stress generated by LSP increases with successive LSP scans and decreases along the depth, with a maximum value of −369 MPa. The hardness on the surface can be improved by 12% using LSP. In situ transmission electron microscopy (TEM) irradiation studies reveal that dislocations and incoherent twin boundaries induced by LSP serve as effective sinks to annihilate irradiation defects. These findings suggest that LSP can improve the mechanical properties and irradiation resistance of ODS austenitic steels in nuclear reactor environments.Laser shock peening (LSP) has been applied to oxide-dispersion-strengthened (ODS) austenitic steels in order to improve the mechanical properties and irradiation resistance. Significant plastic deformation and compressive residual stress are generated by LSP in the near surface, improving the hardness. Dislocations and incoherent twin boundaries induced by LSP can serve as effective sinks to annihilate irradiation defects.
      PubDate: 2017-11-07T11:46:29.396414-05:
      DOI: 10.1002/adem.201700641
       
  • Effect of High-Energy Ball Milling on Mechanical Properties of the Mg–Nb
           Composites Fabricated through Powder Metallurgy Process
    • Authors: Alireza Vahid; Peter Hodgson, Yuncang Li
      Abstract: New biocompatible and biodegradable Mg–Nb composites used as bone implant materials are fabricated through powder metallurgy process. Mg–Nb mixture powders are prepared through mechanical milling and manual mixing. Then, the Mg–Nb composites are fabricated through cold press and sintering processes. The effect of mechanical milling and Nb particles as reinforcements on the microstructures and mechanical properties of Mg–Nb composites are investigated. The mechanical milling process is found to be effective in reducing the size of Mg and Nb particles, distributing the Nb particles uniformly in the Mg matrix and obtaining Mg–Nb composite particles. The Mg–Nb composite particles can be bound together firmly during the sintering process, result in Mg–Nb composite structures with no intermetallic formation, lower porosity, and higher mechanical properties compared to composites prepared through manual mixing. Interestingly, the mechanical properties of manually mixed Mg–Nb composites appear to be even lower than that of pure Mg.New biodegradable Mg–Nb composites are fabricated through powder metallurgy process. The effect of mechanical milling and Nb particles as reinforcements on the microstructures and mechanical properties of the composites are investigated. The mechanical milling reduces the size of Mg and Nb particles and distributes the Nb particles uniformly in the Mg matrix, produces composites with low porosity and high mechanical properties.
      PubDate: 2017-11-06T04:27:47.527067-05:
      DOI: 10.1002/adem.201700759
       
  • Vibration Damping of Carbon Nanotube Assembly Materials
    • Authors: Jingna Zhao; Fulin Wang, Xin Zhang, Linjie Liang, Xueqin Yang, Qingwen Li, Xiaohua Zhang
      Abstract: Vibration reduction is of great importance in various engineering applications, and a material that exhibits good vibration damping along with high strength and modulus has become more and more vital. Owing to the superior mechanical property of carbon nanotube (CNT), new types of vibration damping material can be developed. This paper presents recent advancements, including our progresses, in the development of high-damping macroscopic CNT assembly materials, such as forests, gels, films, and fibers. In these assemblies, structural deformation of CNTs, zipping and unzipping at CNT connection nodes, strengthening and welding of the nodes, and sliding between CNTs or CNT bundles are playing important roles in determining the viscoelasticity, and elasticity as well. Toward the damping enhancement, strategies for micro-structure and interface design are also discussed.Carbon nanotube (CNT) assembly materials are superior vibration damping materials, with performance better than conventional metal and polymer materials. The interface engineering between CNTs and at CNT connection nodes is the key to tune the damping performance. This review addresses the recent progresses on the vibrational properties of CNT forests, gels, films, and fibers.
      PubDate: 2017-11-06T04:26:51.449241-05:
      DOI: 10.1002/adem.201700647
       
  • Microstructure and Tribological Behavior of Stripe Patterned TiN Film
           Prepared with Filtered Cathodic Vacuum Arc Deposition (FCVAD)
    • Authors: Ping Chen; Yingqian La
      Abstract: This paper describes an experimental investigation into the influence of the stripe interspace and applied load on the tribological behavior of stripe patterned TiN films. The stripe patterned TiN films are deposited on an H13 steel surface by masked deposition with the filtered cathodic vacuum arc discharge (FCVAD) technique. The surface micro morphology, chemical composition, crystal structure, and mechanical properties of the films is characterized using 3D white light interferometry, scanning electron microscopy (SEM), X-ray diffractometry (XRD), and a nano-indentation tester, respectively. The tribological performance of patterned TiN is measured using a UMT-5 tribometer, and the friction and wear mechanisms are analyzed, compared with that of the full TiN film and H13 steel substrate. The results show that the stripe patterned TiN films has better tribological properties than the full TiN film. These results are attributed to the synergistic effect between the surface pattern and the TiN film. The stripe interspace and the applied load has a more significant effect on the wear rate of the stripe patterned TiN films than the coefficient of friction of their friction pairs. A further study, however, is needed to analyze the relationship between the applied load and the wear rates of the stripe patterned TiN films.This paper describes an experimental investigation into the influence of the stripe interspace and applied load on the tribological behavior of stripe patterned TiN films. The stripe patterned TiN films are prepared by masked deposition using filtered cathodic vacuum arc discharge technique.
      PubDate: 2017-11-02T08:51:05.514755-05:
      DOI: 10.1002/adem.201700700
       
  • Compositional and Tribo-Mechanical Characterization of Ti-Ta Coatings
           Prepared by Confocal Dual Magnetron Co-Sputtering
    • Authors: Amin Bahrami; Jonatán Pérez Álvarez, Osmary Depablos-Rivera, Roberto Mirabal-Rojas, Agustin Ruíz-Ramírez, Stephen Muhl, Sandra E. Rodil
      Abstract: Titanium-Tantalum coatings are deposited by magnetron co-sputtering technique, using independently driven titanium and tantalum targets. The effect of the Ta content on the structure, mechanical, and wear properties of Ti films is investigated. It is found that the percentage of the added Ta varies linearly from 3.7 to 31.3 at% by increasing the power applied to the Ta target from 10 to 100 W. The XRD results show that the coatings are crystalline, and there is no evidence of the formation of intermetallic phases, instead formation of metastable phases of α″ and β depending on Ta content are observed, though the samples are deposited at low temperature (150 °C). It is shown that the elastic strain to failure (H/Er; hardness to reduced elastic moduli ratio) can be increased by 40% through the formation of crystalline phases with a lower E, while the hardness remains constant. The tribological study shows that increasing the Ta content up to 14.9 at% causes a significant improvement in adhesion of the coating to a soft metallic substrate.The production of nanostructured, hard, and tough metallic coatings using vapor deposition method is of increasing interests in the coating of metallic substrates. The results in this study show that addition of Ta to the Ti coatings improves the toughness and adhesion of coatings to the substrate, although it has not significant effect on the hardness of coatings.
      PubDate: 2017-11-02T04:05:58.465537-05:
      DOI: 10.1002/adem.201700687
       
  • Directly Verifiable Neutron Diffraction Technique to Determine Retained
           Austenite in Steel
    • Authors: Tatiana Lychagina; Alexander Zisman, Ekaterina Yashina, Dmitry Nikolayev
      Abstract: Conventional procedures for quantitative analysis of retained austenite in steels by neutron diffraction ignore the effect of crystallographic texture and rely on a-priori parameters rather than a direct calibration with appropriate etalons. As the main drawback, this method is not directly verified by independent data. In order to get over the verification problem, that is, to calibrate the method, reference sandwich-like samples with predefined amounts of austenite have been prepared. Neutron diffraction allows to measure large samples from one hand and to get rid of the texture influence from the other. Application of the proposed method was illustrated by volume fractions of retained austenite determination in medium-carbon martensitic steel tempered at various temperatures. Main result of our work is the developed method based on complete orientation averaging by means of neutron diffraction and usage of the calibration samples. It allowed to refine the austenite detectability limit to about 0.1% (vol.). Based on the method calibration, low fractions of retained austenite (0.13–2.9%) have been determined in the medium-carbon martensitic steel tempered at various temperatures.The new method of the quantitative analysis for retained austenite in steels by neutron diffraction is proposed. This approach is based on the calibration with reference samples in order to reliably evaluate low fractions of retained austenite in textured steels with detectability limit refined to 0.1%. The suggested method implies direct verification of the results.
      PubDate: 2017-10-30T07:41:46.467493-05:
      DOI: 10.1002/adem.201700559
       
  • Ultra-Smooth, Chemically Functional Silica Surfaces for Surface
           Interaction Measurements and Optical/Interferometry-Based Techniques
    • Authors: Howard A. Dobbs; Yair Kaufman, Jeff Scott, Kai Kristiansen, Alex M. Schrader, Szu-Ying Chen, Peter Duda, Jacob N. Israelachvili
      Abstract: The study of interfacial phenomena is central to a range of chemical, physical, optical, and electromagnetic systems such as surface imaging, polymer interactions, friction/wear, and ion-transport in batteries. Studying intermolecular forces and processes of interfaces at the sub-nano scale has proven difficult due to limitations in surface preparation methods. Here, we describe a method for fabricating reflective, deformable composite layers that expose an ultra-smooth silica (SiO2) surface (RMS roughness
      PubDate: 2017-10-30T06:25:58.062495-05:
      DOI: 10.1002/adem.201700630
       
  • Experimental Study on the Effect of Cooling Rate on the Secondary Phase in
           As-Cast Mg–Gd–Y–Zr Alloy
    • Authors: Keyan Wu; Xuyang Wang, Lv Xiao, Zhongquan Li, Zhiqiang Han
      Abstract: The effect of cooling rate on the composition, morphology, size, and volume fraction of the secondary phase in as-cast Mg–Gd–Y–Zr alloy is investigated. In the study, a casting containing five steps with thickness of 10–50 mm is produced, in which cooling rate ranging from 2.6 to 11.0 K s−1 is created. The secondary phase is characterized using optical microscope (OM), scanning electron microscope (SEM), and electron probe micro-analyzer (EPMA). The volume fraction of the secondary phase is determined using OM and quantitative metallographic analysis, and Vickers hardness test is conducted to verify the analysis results. The effect of the cooling rate on the volume fraction of the secondary phase is discussed in detail. The result shows that with the increase of the cooling rate, the size of the secondary phase decreases. The effect of the cooling rate on the volume fraction of the secondary phase is complicated somewhat. A comprehensive analysis on the experimental data shows that a critical cooling rate may exist, over which the volume fraction of the secondary phase decreases with the increase of the cooling rate, however under which the volume fraction increases with the increase of the cooling rate.The effect of cooling rate on the composition, morphology, size, and volume fraction of the secondary phase in as-cast Mg–Gd–Y–Zr alloy is investigated. The mechanisms governing the variation of the volume fraction of the secondary phase with cooling rates are revealed.
      PubDate: 2017-10-30T01:41:32.854279-05:
      DOI: 10.1002/adem.201700717
       
  • Friction Reduction Induced by Elliptical Surface Patterns under Lubricated
           Conditions
    • Authors: Andreas Rosenkranz; Adam Szurdak, Philipp G. Grützmacher, Gerhard Hirt, Frank Mücklich
      Abstract: Recording Stribeck-like curves is an efficient way to evaluate the frictional performance and efficiency of patterned surfaces. Elliptical patterns with varying area density and structural depth are fabricated by micro-coining on steel substrates (AISI 304). A ball-on-disc tribometer is used to perform unidirectional sliding experiments for the polished reference and the elliptical patterns dependent on the sliding velocity. In this study, a clear connection between structural parameters such as length of long and short axis, aspect ratio, and pitch with the frictional behavior can be found. Comparing patterns with comparable depth and area density underlines that elliptical patterns having larger individual features (increased length of both axes) separated by a larger pitch reduce the COF more significantly. The number of tribologically active individual elliptical structures, recirculation effects of the lubricant, as well as the pattern geometry that may lead to undesired edge effects and stress concentrations need to be taken into consideration to explain those findings. The sample with the smallest structural depth, the smallest area density, and the lowest aspect ratio (A1) leads to the maximum friction reduction (4-fold) for all velocities which underlines the enormous potential of elliptical structures in terms of friction reduction.The frictional performance of elliptical surface patterns fabricated by hot micro-coining is investigated by recording Stribeck-like curves. The sample with the smallest structural depth, the smallest area density, and the lowest aspect ratio lead to the maximum friction reduction by a factor of 4, which underlines the enormous potential of elliptical structures in terms of friction reduction.
      PubDate: 2017-10-25T09:55:36.549437-05:
      DOI: 10.1002/adem.201700731
       
  • Fabrication and Optical Properties of Periodic Ag Nano-Pore and
           Nano-Particle Arrays with Controlled Shape and Size over Macroscopic
           Length Scales
    • Authors: Colm T. Mallon; Kiang W. Kho, Houda Gartite, Robert J. Foster, Tia E. Keyes
      Abstract: A facile and economical route to preparation of highly ordered sliver pore or particle arrays with controlled pore-shape and size extended over cm2 areas is described. The substrates are prepared at planar and curved surfaces via sphere-imprinted polymer (PDMS) templating using polystyrene spheres with diameters of 820, 600, or 430 nm. Nano-pore arrays are created by sputtering 80 nm of Ag directly onto the templates and nano-particle arrays are prepared by electrode-less deposition of Ag from Tollen's reagent. The shape of the nano-pore or particles in the array conformed to that of the imprint of the sphere on the template. Stretching the flexible template enable creation of cuboid shaped nano-voids and nano-particles following Ag deposition. Diffuse reflectance from the spherical Ag nano-cavity arrays showed absorbance maxima at wavelengths comparable similar to the diameter of the templating sphere, whereas reflectance from the cuboid arrays, showed little correlation with the sphere diameter. The cuboid nano-particle arrays showed the most intense visible absorption which is red-shifted compared to the spherical arrays. White light diffraction from the arrays, observed by rotating 1 cm2 substrates relative to a fixed light source, reflected exactly the symmetry axes of the periodic nano-features in the arrays demonstrating the remarkable macroscopic order of the periodic structures. Raman spectra of 1-benzenethiol adsorbed at the arrays indicated SERS enhancements from the substrates are attributed mainly to surface nano-roughness with only moderate contributions from the periodically corrugated structures. Despite excitation at the major resonance dip in the reflectance spectrum, a weak, localized rim dipole mode is found to elicit a small increase in the SERS enhancement factor for the 430 nm diameter spherical arrays. FDTD studies of nano-void arrays provided insights into various factors affecting the SERS experiment and confirmed the array's plasmonic spectra are dominated by propagating plasmon modes under microscope excitation/collection angles.In this paper, a facile and economical route to preparation of highly ordered silver nano-pore arrays via sphere imprinted PDMS templating is described. We demonstrated that a series of various pore-shapes, ranging from spherical and cuboid, can be obtained by stretching the polymer template. FDTD simulation is also carried out to provide insights into the plasmonic origin of the observed SERS enhancements.
      PubDate: 2017-10-24T11:53:03.324955-05:
      DOI: 10.1002/adem.201700532
       
  • Front Cover: Advanced Engineering Materials 10∕2017
    • Abstract: The cover image, derived from a microcomputed tomography analysis and treated with a threshold based skeletonization process, shows the hierarchical pore network of an alumina foam. Thickness and color indicate different pore diameters; red: high value, blue: low value. The thickness is scaled by factor 0.2 to enable an insight 3D-view. More details can be found in the article 1700369 by Michael Scheffler and co-workers.
      PubDate: 2017-10-23T11:19:05.236702-05:
      DOI: 10.1002/adem.201770034
       
  • Masthead: Adv. Eng. Mater. 10∕2017
    • PubDate: 2017-10-23T11:19:04.950355-05:
      DOI: 10.1002/adem.201770035
       
  • Contents: Adv. Eng. Mater. 10∕2017
    • PubDate: 2017-10-23T11:19:00.902752-05:
      DOI: 10.1002/adem.201770036
       
  • Editorial for the Special Issue "Cellmat 2016"
    • Authors: Olaf Andersen; Michael Scheffler
      PubDate: 2017-10-23T11:19:00.835229-05:
      DOI: 10.1002/adem.201700749
       
  • The Influence of Hydrogen on the Low Cycle Fatigue Behavior of Medium
           Strength 3.5NiCrMoV Steel Studied Using Notched Specimens
    • Authors: Qian Liu; Andrej Atrens
      Abstract: The influence of hydrogen on low cycle fatigue (LCF) of 3.5NiCrMoV steel electrochemically hydrogen charged in the acidified pH 2 0.1 M Na2SO4 solution is studied. In the presence of hydrogen, the fatigue life decreases significantly by ≈70 to ≈80% by: (i) the crack initiation period is decreased; and (ii) the crack growth rate is accelerated. SEM observation indicates that in the presence of hydrogen, the fracture surface shows flat transgranular fracture with vague striations and some intergranular fracture at lower stresses. The fatigue crack growth rate increases with increasing cyclic stress amplitude and with hydrogen fugacity. Once the fatigue crack reaches a critical length, the specimen becomes mechanical unstable and fracture due to ductile overload occurs. The hydrogen contribution to the final fracture process is not significant.The influence of hydrogen on low cycle fatigue of 3.5NiCrMoV steel electrochemically hydrogen charged is studied. In the presence of hydrogen, the fatigue life decreases significantly by ≈70–80% (as illustrated in the figure) by: (i) the crack initiation period is decreased; and (ii) the crack growth rate is accelerated.
      PubDate: 2017-10-23T08:05:45.765029-05:
      DOI: 10.1002/adem.201700680
       
  • Challenges of Diffusion Bonding of Different Classes of Stainless Steels
    • Authors: Thomas Gietzelt; Volker Toth, Andreas Huell
      Abstract: Solid state diffusion bonding is used to produce monolithic parts exhibiting mechanical properties comparable to those of the bulk material. This requires diffusion of atoms across mating surfaces at high temperatures, accompanied by grain growth. In case of steel, polymorphy helps to limit the grain size, since the microstructure is transformed twice. The diffusion coefficient differs extremely for ferritic and austenitic phases. Alloying elements may shift or suppress phase transformation until the melting range. In this paper, diffusion bonding experiments are reported for austenitic, ferritic, and martensitic stainless steels possessing varying alloying elements and contents. Passivation layers of different compositions are formed, thus affecting the local diffusion coefficient and impeding diffusion across faying surfaces. As a consequence, different bonding temperatures are needed to obtain good bonding results, making it difficult to control the deformation of parts, since strong nonlinearities exist between temperature, bonding time, and bearing pressure. For martensitic stainless steel, it is shown that it is very easy to obtain good bonding results at low deformation, whereas ferritic and austenitic stainless steels require much more extreme bonding parameters.Diffusion bonding is employed for full cross-sectional joining of complex geometries. The graphical abstract shows a part for ITER (International Thermonuclear Experimental Reactor) made of austenitic stainless steel, containing 3D cooling structures. Thermally stable passivation layers make it difficult to form a monolithic part. Employing a self-stabilizing design, the bonding area is increased with process time, allowing to control deformation.
      PubDate: 2017-10-23T00:20:58.312674-05:
      DOI: 10.1002/adem.201700367
       
  • Fragmentation of α Grains Accelerated by the Growth of β Phase in
           Ti–5Al–2Sn–2Zr–4Mo–4Cr during Hot Deformation
    • Authors: Jin-Zhao Sun; Miao-Quan Li, Hong Li
      Abstract: The fragmentation of elongated α grains accelerated by the growth of β phase in Ti–5Al–2Sn–2Zr–4Mo–4Cr during hot deformation was examined using electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM). It was determined that boundary splitting resulted in the fragmentation of αE. The kinked sharp α grains, which were formed with help of “civilian” growth of β phase, are necessary structures for the fragmentation of elongated α grains. In addition, the texture results showed an initial deviation from Burgers orientation relationship (OR) in α/β interphase boundaries, indicating that the “civilian” growth of the β phase based on the pre-existing β grain boundaries implied a constant loss of coherency in α/β interphase boundaries, which also accelerated the fragmentation of elongated α grains.The “civilian” growth of the β phase preferentially occurs in the location surrounded by DT, which promotes the formation of groove that plays an important role in the fragmentation of αE. The “ civilian” growth of the β phase based on the pre-existing β grain boundaries, suggesting a constant deviation from Burgers OR in α/β interphase boundaries, also accelerates the fragmentation of αE.
      PubDate: 2017-10-20T03:15:42.869267-05:
      DOI: 10.1002/adem.201700200
       
  • High-Entropy Alloys: Potential Candidates for High-Temperature
           Applications – An Overview
    • Authors: Sathiyamoorthi Praveen; Hyoung Seop Kim
      Abstract: Multi-principal elemental alloys, commonly referred to as high-entropy alloys (HEAs), are a new class of emerging advanced materials with novel alloy design concept. Unlike the design of conventional alloys, which is based on one or at most two principal elements, the design of HEA is based on multi-principal elements in equal or near-equal atomic ratio. The advent of HEA has revived the alloy design perception and paved the way to produce an ample number of compositions with different combinations of promising properties for a variety of structural applications. Among the properties possessed by HEAs, sluggish diffusion and strength retention at elevated temperature have caught wide attention. The need to develop new materials for high-temperature applications with superior high-temperature properties over superalloys has been one of the prime concerns of the high-temperature materials research community. The current article shows that HEAs have the potential to replace Ni-base superalloys as the next generation high-temperature materials. This review focuses on the phase stability, microstructural stability, and high-temperature mechanical properties of HEAs. This article will be highly beneficial for materials engineering and science community whose interest is in the development and understanding of HEAs for high-temperature applications.In recent years, high entropy alloys (HEAs) receive wide attention due to its unique alloy design concept and outstanding properties. This review presents a general overview of HEAs as a potential candidate for high-temperature applications. The need for the profound research on the high-temperature properties of HEAs is highlighted.
      PubDate: 2017-10-18T06:35:39.302184-05:
      DOI: 10.1002/adem.201700645
       
  • Study of Fatigue Behavior of Epoxy-Carbon Composites under Mixed Mode I/II
           Loading
    • Authors: Clara Rocandio; Jaime Viña, Antonio Argüelles, Silvia Rubiera
      Abstract: This paper presents an experimental assessment of the initiation and propagation of interlaminar cracks under mixed mode I/II dynamic fracture loading of a composite material with an MTM45-1 epoxy matrix and unidirectional IM7 carbon-fiber reinforcement. The aims of the experimental program developed for this purpose are to determine, on the one hand, the initiation curves of the fatigue delamination process, understood as the number of load cycles needed to generate a fatigue crack, and on the other, the crack growth rate (delamination rate) for different percentages of static Gc, in both cases for two mode mixities (0.2 and 0.4) and for a tensile ratio R = 0.1. All this with the goal of quantifying the influence of the degree of mode mixity on the overall behavior of the laminate under fatigue loading. The results show that the energy release rate increases with increasing loading levels for both degrees of mode mixity and that the fatigue limit is located around the same percentages. However, crack growth rate behavior differs from one degree of mode mixity to the other. This difference in the behavior of the material may be due to the varying influence of mode I loading on the delamination process.The initiation curves of the fatigue delamination process of a composite materials with an MTM45-1 epoxy matrix and unidirectional IM7 carbon-fiber reinforcements have been obtained for two mode mixities and for a tensile ratio. Crack growth rate behavior differs from one degree of mode mixity to the other, being the cause the varying of mode I loading on the delamination process.
      PubDate: 2017-10-18T06:30:40.214583-05:
      DOI: 10.1002/adem.201700569
       
  • Reactive Structural Materials: Preparation and Characterization
    • Authors: Daniel L. Hastings; Edward L. Dreizin
      Abstract: Reactive structural materials, which can serve both as structural elements as well as a source of chemical energy released upon initiation have emerged as an important class of metal-based composites for use in various energetic systems. Such materials rely on a variety of exothermic reactions, from oxidation to formation of metal-metalloid and intermetallic phases. The rates of these reactions are as important as the energy that may be released, in order for them to occur at the time scales compatible with the requirements of applications. Therefore, chemical composition, scale at which reactive components are mixed, and the structure and morphology of materials are important and can be controlled by the method of preparation and compaction of the composite materials. Methods of preparation of the composite structures are briefly reviewed as well as methods of characterization of their mechanical and energetic properties. In addition to common thermo-analytical and static mechanical property measurements, dynamic tests of mechanical properties as well as ignition and combustion experiments are necessary to understand the fragmentation, initiation, and heat release expected for these materials when they are stimulated by an impact, shock, or rapid heating. Reaction mechanisms are studied presently for the thin layers and small samples of reactive materials initiated in carefully designed experiments. In other experiments, impact and explosive initiation are characterized for larger material compacts in the conditions imitating practical scenarios. Examples of results describing thermal, impact, and explosive initiation of some of the reactive materials are presented.Reactive structural materials serve both as structural elements and a source of chemical energy released upon initiation. Chemical composition, scale at which reactive components are mixed, and the structure of materials are controlled by the method of preparation and compaction of the composites. Material types, their synthesis and methods of characterization of their mechanical and energetic properties are reviewed.
      PubDate: 2017-10-17T07:46:53.032036-05:
      DOI: 10.1002/adem.201700631
       
  • Liquid PMMA: A High Resolution Polymethylmethacrylate Negative Photoresist
           as Enabling Material for Direct Printing of Microfluidic Chips
    • Authors: Frederik Kotz; Karl Arnold, Stefan Wagner, Werner Bauer, Nico Keller, Tobias M. Nargang, Dorothea Helmer, Bastian E. Rapp
      Abstract: Polymethymethacrylate (PMMA) is one of the most important thermoplasts and a commonly used material in microsystem fabrication, for example, microfluidics owning mainly to its optical transparency, biocompatibility, low autofluorescence, and low cost. However, being a thermoplastic material PMMA is typically structured using industrial replication techniques making PMMA unsuitable for rapid prototyping. The fact that neither material nor processing technique can be directly transferred from laboratory to industrial state makes the research-to-business conversion often extremely difficult in microfluidics since material properties have a major impact on the final system behavior. This paper presents “Liquid PMMA,” a fast curing viscous PMMA prepolymer which can be used as a negative photoresist and directly structured using ultraviolet or visible light with tens of micron resolution and smooth surfaces. Using this technique microfluidic chips in PMMA can be fabricated within minutes. The cured Liquid PMMA parts show the same high optical transparency, low autofluorescence, and surface properties like commercial PMMA. In this way, microfluidic chips can be rapidly developed and optimized on the laboratory scale in the same material which is later on used on the industrial scale.Polymethylmethacrylate (PMMA) is an important industrial material for microfluidics owing mainly to its optical transparency, biocompatibility, and low cost. We present “Liquid PMMA,” a fast curing PMMA prepolymer which can be used as a negative photoresist and directly structured by light. PMMA microchips can be structured within minutes.
      PubDate: 2017-10-17T07:45:40.963088-05:
      DOI: 10.1002/adem.201700699
       
  • Using Post-Deformation Annealing to Optimize the Properties of a ZK60
           Magnesium Alloy Processed by High-Pressure Torsion
    • Authors: Seyed A. Torbati-Sarraf; Shima Sabbaghianrad, Terence G. Langdon
      Abstract: A ZK60 magnesium alloy with an initial grain size of ≈10 µm is processed by high-pressure torsion (HPT) through 5 revolutions under a constant compressive pressure of 2.0 GPa with a rotation speed of 1 rpm. An average grain size of ≈700 nm is achieved after HPT with a high fraction of high-angle grain boundaries. Tensile experiments at room temperature show poor ductility. However, a combination of reasonable ductility and good strength is achieved with post-HPT annealing by subjecting samples to high temperatures in the range of 473–548 K for 10 or 20 min. The grain size and texture changes are also examined by electron back scattered diffraction (EBSD) and the results compared to long-term annealing for 2500 min at 450 K. The results of this study suggest that a post-HPT annealing for a short period of time may be effective in achieving a reasonable combination of strength and ductility.The production of ultrafine grained structure through the severe plastic deformation processes is of increasing interests in lightweight materials. Magnesium alloys show poor ductility at room temperature after severe plastic deformation. The results of this study suggest that a post-HPT annealing for a short period of time can be effective in achieving a reasonable combination of strength and ductility.
      PubDate: 2017-10-16T01:46:40.061658-05:
      DOI: 10.1002/adem.201700703
       
  • Nature-Inspired Lightweight Cellular Co-Continuous Composites with
           Architected Periodic Gyroidal Structures
    • Authors: Oraib Al-Ketan; Ahmad Soliman, Ayesha M. AlQubaisi, Rashid K. Abu Al-Rub
      Abstract: Shell-core cellular composites are a unique class of cellular materials, where the base constituent is made of a composite material such that the best distinctive physical and/or mechanical properties of each phase of the composite are employed. In this work, the authors demonstrate the additive manufacturing of a nature inspired cellular three-dimensional (3D), periodic, co-continuous, and complex composite materials made of a hard-shell and soft-core system. The architecture of these composites is based on the Schoen's single Gyroidal triply periodic minimal surface. Results of mechanical testing show the possibility of having a wide range of mechanical properties by tuning the composition, volume fraction of core, shell thickness, and internal architecture of the cellular composites. Moreover, a change in deformation and failure mechanism is observed when employing a shell-core composite system, as compared to the pure stiff polymeric standalone cellular material. This shell-core configuration and Gyroidal topology allowed for accessing toughness values that are not realized by the constituent materials independently, showing the suitability of this cellular composite for mechanical energy absorption applications.The figure shows designed and 3D printed architected co-continuous composites with rigid shell and soft core configuration. The proposed co-continuous composite employs a topology-property relationship that allows controlling the mechanical and physical properties by tuning its architecture.
      PubDate: 2017-10-16T01:05:42.596707-05:
      DOI: 10.1002/adem.201700549
       
  • Novel 3D-Printed Hybrid Auxetic Mechanical Metamaterial with
           Chirality-Induced Sequential Cell Opening Mechanisms
    • Authors: Yunyao Jiang; Yaning Li
      Abstract: New hybrid auxetic chiral mechanical metamaterial are designed and fabricated via multi-material 3D printing. Due to the chirality-induced rotation, the material have unique sequential cell-opening mechanisms. Mechanical experiments on the 3D printed prototypes and systematic FE simulations show that the effective stiffness, the Poisson's ratio and the cell-opening mechanisms of the new design can be tuned in a very wide range by tailoring two non-dimensional parameters: the cell size ratio and stiffness ratio of component materials. As example applications, sequential particle release mechanisms and color changing mechanisms of the new designs are also systematically explored. The present new design concepts can be used to develop new multi-functional smart composites, sensors and/or actuators which are responsive to external load and/or environmental conditions for applications in drug delivery and color changing for camouflage.Novel hybrid auxetic chiral mechanical metamaterial are designed and fabricated via multi-material 3D printing. Due to chirality-induced rotation, the new auxetic mechanical metamaterials have unique sequential cell-opening mechanisms under uni-axial tension. As demos, the present new design concepts are used to develop multi-functional smart materials for sequential particle release and color changing for camouflage.
      PubDate: 2017-10-11T08:10:42.053775-05:
      DOI: 10.1002/adem.201700744
       
  • Mechanical and Electromagnetic Interference Shielding Behavior of C/SiC
           Composite Containing Ti3SiC2
    • Authors: Xiaomeng Fan; Xiaowei Yin, Yanzhi Cai, Litong Zhang, Laifei Cheng
      Abstract: In order to obtain the composites with the integration of structural and functional properties, Ti3SiC2 is introduced into C/SiC due to its excellent damage tolerance and electromagnetic interference (EMI) shielding properties. C/SiC–Ti3SiC2 has the lower tensile strength, while the higher compressive strength than C/SiC. The penetration energy of C/SiC–Ti3SiC2 in the impact experiment is improved at least three times than that of C/SiC, resulting from the improved damage tolerance. With the introduction of Ti3SiC2, the EMI shielding effectiveness increases from 31 to 41 dB in X-band (8.2 to 12.8 GHz) due to the increase of electrical conductivity. C/SiC–Ti3SiC2 reveals the great potential as structural and functional materials based on the multi-functional properties.With the introduction of Ti3SiC2 by liquid silicon infiltration, the dense inter-bundle matrix with high damage-tolerance and electrical-conductivity can be obtained for C/SiC–Ti3SiC2, resulting in the better compressive strength, impact resistance, and electromagnetic interference shielding properties than those of C/SiC, which reveals the great potential as structural and functional materials.
      PubDate: 2017-10-11T08:01:15.82601-05:0
      DOI: 10.1002/adem.201700590
       
  • Influences of Friction Stir Welding and Post-Weld Heat Treatment on
           Al–Cu–Li Alloy
    • Authors: Yi Lin; Change Lu, Chengyang Wei, Ziqiao Zheng
      Abstract: In this paper, the influences of friction stir welding (FSW) and post-weld heat treatment (PWHT) on the microstructures and tensile properties of Al–Cu–Li alloy are investigated. After FSW, strengthen loss occurred in the welding area. Remarkable softening occurs in the thermo-mechanically affected zone (TMAZ) resulting from dissolution of Al3Li (δ′) phases. Recrystallization and precipitation of ultra-fine δ′ phases take place in the nugget zone (NZ) that lightens the softening degree of this zone. A noteworthy enhancement in the hardness and tensile strength of the joint is achieved after T8 re­aging treatment (3% − pre-deformation, 30 h at 152 °C). However, re-solution treatment coupled with re-aging treatment leads to ductility deterioration in the joint because coplanar slip of coarse Al3Li phases induces severe stress concentration during plastic deformation.The paper investigates the microstructure and mechanical properties evolution of Al–Cu–Li alloy during FSW and PHWTs. The results show that dissolution of strengthening phases induces the strength loss after FSW, and the T8 re-aging treatment can effectively enhances the strength of joint without the ductility being excessively deteriorated.
      PubDate: 2017-10-10T06:21:18.021152-05:
      DOI: 10.1002/adem.201700652
       
  • 3-D Printing and Development of Fluoropolymer Based Reactive Inks
    • Authors: Fidel D. Ruz-Nuglo; Lori J. Groven
      Abstract: Engineering reactive materials is an ever present goal in the energetics community. The desire is to have energetics configured in such a manner that performance is tailored and energy delivery can be targeted. Additive manufacturing (3-D printing) is one area that could significantly improve our capabilities in this area, if adequate formulations are developed. In this paper, fluoropolymer based reactive inks are developed with micron (mAl) and nanoscale aluminum (nAl) serving, as the fuel at high solids loading (up to 67 wt%) and their viscosity required for 3-D printing is detailed. For the pen-type technique and valves used in this work, it is required to have viscosities on the order of 104–105 cP. For printed traces with apparent diameters under
      PubDate: 2017-10-09T07:10:53.772388-05:
      DOI: 10.1002/adem.201700390
       
  • Galvanic Corrosion and Mechanical Behavior of Fiber Metal Laminates of
           Metallic Glass and Carbon Fiber Composites
    • Authors: Lee Hamill; Douglas C. Hofmann, Steven Nutt
      Abstract: The possibility of galvanic corrosion typically prohibits the pairing of carbon fiber and aluminum in a fiber metal laminate (FML). In this study, the authors describe a new type of FML comprised of alternating layers of bulk metallic glass (BMG) and carbon fiber reinforced polymer (CFRP) composite. The authors compare the galvanic coupling and mechanical behavior of an Al-based FML and a BMG-CFRP FML. Results show that when paired with CFRPs, BMG exhibits far less galvanic corrosion than aluminum paired with CFRP. In fact, the corrosion between BMG and CFRP is similar in magnitude to the corrosion between aluminum and glass fiber, the two constituent materials of GLARE, the most widely used FML. While interlaminar shear strength and flexural strength are similar for both FML types, the tensile strength and modulus of BMG-based FMLs are greater than those of Al-based FMLs.The galvanic corrosion resistance and mechanical performance of two fiber metal laminates are compared. Results show negligible galvanic corrosion and increased tensile strength and modulus in BMG-CFRP laminates when compared to AL-CFRP counterparts. To date, very few galvanic corrosion resistant options exist for CFRP-based FMLs, and the results of this study expand those options.
      PubDate: 2017-10-09T02:25:49.736964-05:
      DOI: 10.1002/adem.201700711
       
  • Optimization of Composite Foam Concept for Protective Helmets to Mitigate
           Rotational Acceleration of the Head in Oblique Impacts: A Parametric Study
           
    • Authors: Yasmine Mosleh; Leonard Pastrav, Aart Willem van Vuure, Bart Depreitere, Jos Vander Sloten, Jan Ivens
      Abstract: Rotational acceleration of the head is known to be the cause of traumatic brain injuries. It was hypothesized that by introducing anisotropy in a foam liner in head protection applications, for example, protective helmets, rotational acceleration transmitted to the head can be further mitigated. Therefore, composite foam with a cylinder/matrix configuration with anisotropy at “macro level” is proposed as a smart structural solution to replace single layer foam headliners of the same weight and thickness. In this paper, a parametric study on the cylinder/matrix configuration is performed and the results are compared with these of single layer expanded polystyrene foam. The structure is subsequently optimized for the best performance in mitigation of rotational acceleration and velocity. Oblique impact results show that the parameters such as the number of cylinders in a given structure, and the compliance of the matrix foam significantly affect the extent of rotational acceleration and velocity mitigation. Optimized composite foam configurations are subsequently proposed and they demonstrate a mitigation of rotational acceleration and velocity up to 44 and 19%, respectively. Moreover, relevant global head injury criteria such as HIC (Head Injury Criterion), RIC (Rotational Injury Criterion), HIPmax (Head Impact Power), GAMBIT (Generalised Acceleration Model for Brain Injury Threshold), and BrIC (Brain Injury Criterion) demonstrated reduction up to 27, 67, 31, 26, and 19%, respectively.In this paper, a parametric study on composite foam with cylinder/matrix configuration is performed to optimize the structure for mitigation of head rotational acceleration during oblique impact. The results show that parameters such as the number of cylinders in the structure, and the compliance of the matrix foam significantly affect the extent of mitigation of head rotational acceleration.
      PubDate: 2017-10-09T02:25:37.747543-05:
      DOI: 10.1002/adem.201700443
       
  • The Fabrication and Characterization of Bimodal Nanoporous Si with
           Retained Mg through Dealloying
    • Authors: Tyler L. Maxwell; T. John Balk
      Abstract: The fabrication and characterization of bimodal nanoporous silicon films with retained magnesium, achieved through a novel approach utilizing free corrosion dealloying of precursor Si–Mg films in distilled water, is studied. Investigation of film structure and chemical composition using various techniques reveals important characteristics potentially relevant to lithium-ion battery applications. Dealloying of precursor films results in a hierarchal structure, where larger ligaments have an average width of 83 nm and smaller ligaments an average width of 19 nm. A thin, porous surface layer is present on most dealloyed films and is largely composed of magnesium and silicon oxides, as verified by XPS surface analysis. TEM studies reveal that as-dealloyed films are amorphous, but nanocrystalline silicon grains form after vacuum annealing at 500 °C. EDS mapping and XPS reveal three distinct chemical composition regions through the film thickness, where residual magnesium generally increases as a function of film thickness, with the highest amount of retained magnesium at the surface. The ligament size, composition, and structure, combined with the simple, non-hazardous nature of the dealloying method, make this an attractive material and processing technique for efficient and scalable production of lithium-ion battery anode material.This paper presents a facile approach to create bimodal nanoporous silicon films with residual magnesium, by dealloying sputter-deposited silicon-magnesium precursors in distilled water. The microstructure of films before and after annealing is characterized with SEM and TEM, while chemical composition is analyzed with EDS and XPS surface analysis. This material's characteristics make it a promising candidate for lithium–ion battery applications.
      PubDate: 2017-10-09T01:25:42.579217-05:
      DOI: 10.1002/adem.201700519
       
  • Rationally Designed Silicon Nanostructures as Anode Material for
           Lithium-Ion Batteries
    • Authors: Tong Shen; Zhujun Yao, Xinhui Xia, Xiuli Wang, Changdong Gu, Jiangping Tu
      Abstract: Silicon (Si) is promising for high capacity anodes in lithium-ion batteries due to its high theoretical capacity, low working potential, and natural abundance. However, there are two main drawbacks that impede its further practical applications. One is the huge volume expansion generating during lithiation and delithiation progresses, which leads to severe structural pulverization and subsequently rapid capacity fading of the electrode. The other is the relatively low intrinsic electronic conductivity, therefore, seriously impacting the rate performance. In the past decades, numerous efforts have been devoted for improving the cycling stability and rate capability by rational designs of different nanostructures of Si materials and incorporations with some conductive agents. In this review, the authors summarize the exciting recent research works and focus on not only the synthesis techniques, but also the composition strategies of silicon nanostructures. The advantages and disadvantages of the nanostructures as well as the perspective of this research field are also discussed. We aim to give some reference for engineering application on Si anodes in lithium ion batteries.The authors summarize the strategies that developed lately for improving the electrochemical performance of Si materials. Special focus in this review is the recent progresses in the rational fabrication of Si nanostructures with multiple morphologies, including nanoparticles, nanowires, thin films, and porous structures. Moreover, further improvement tactics, such as collaborating with carbonaceous materials, conductive polymers, and alloy materials are also discussed.
      PubDate: 2017-10-05T08:32:53.56802-05:0
      DOI: 10.1002/adem.201700591
       
  • Combined Microwave and Laser Heating for Glazing of 8Y–ZrO2 and
           8Y–ZrO2/ZrSiO4–Composites
    • Authors: Sebastian Lehmann; Jens Böckler, Monika Willert-Porada, Andreas Rosin, Christian Richter
      Abstract: Sintered porous yttria-stabilized zirconia and zirconia composite ceramics with zirconium silicate are surface glazed by Laser-Assisted Microwave Plasma Processing (LAMPP). Suitable process parameters for surface glazing are determined for those ceramics. The plasma process is monitored by means of pyrometry and optical emission spectroscopy. In order to prove the quality of the surface glazing and to characterize hot corrosion resistance, tests with molten vanadium pentoxide are performed. After 4 h of exposure, the penetration depth of the molten salt is investigated as a function of ceramic composition and pre-treatment by glazing. Upon hot corrosion testing of glazed and non-glazed ceramics, the molten vanadium pentoxide reacts selectively with yttrium oxide, forming yttrium vanadate, and causes crack formation in the zirconia ceramics due to transition to monoclinic zirconia. The results for LAMPP-glazed ceramics show, that a surficial melting phase is achieved because process temperatures exceed 3000 °C. Hence, a dense, crack-free and hardness-enhanced surface layer achieves a better resistance to hot corrosion as compared to non-glazed ceramics. Due to LAMPP-glazing, the vanadium ingress is reduced from 33 to 7 μm for yttria-stabilized zirconia and from 104 to 17 μm for zirconia composite ceramic. Reactions and microstructural changes taking place upon LAMP-Processing are discussed.Suitable process parameters for surface glazing by Laser-Assisted Microwave Plasma Processing of sintered porous zirconia-based ceramics are determined. The plasma process is monitored by means of pyrometry and optical emission spectroscopy. Microstructural investigation and phase analysis is performed before and after hot corrosion test with molten vanadium pentoxide. The dense, crack-free surface layer provides a better resistance to hot corrosion.
      PubDate: 2017-10-04T02:56:26.085561-05:
      DOI: 10.1002/adem.201700615
       
  • Synthesis of Composite Nanosheets of Graphene and Boron Nitride and Their
           Lubrication Application in Oil
    • Authors: Yuchen Liu; Srikanth Mateti, Chao Li, Xuequan Liu, Alexey M. Glushenkov, Dan Liu, Lu Hua Li, Daniel Fabijanic, Ying Chen
      Abstract: Composite nanosheets of graphene and boron nitride have been produced in large quantities for the first time using high-energy ball milling in ammonia gas as an exfoliation agent. The anti-wear properties of the composite nanosheets as a lubricant additive are investigated via a four-ball method. The results show that the composite nanosheets are exfoliated from the commercial graphite and h-BN powders and combined into graphene/BN composite nanosheets during the ball milling process. The composite nanosheets formed have diameters larger than 200 nm and consist of heterostructures of approximately 10 monolayers of graphene and BN. The composite nanosheets exhibit better wear resistance and friction reduction properties than the homogeneous nanosheets because of the stronger interaction between graphene and BN nanosheets, which can effectively improve the anti-wear properties of mineral base oil as a lubricant additive.The graphene/BN composite nanosheets produced by gas-assisted ball milling process form a protection film on the testing material surface leading to a lower friction coefficient and improved anti-wear properties.
      PubDate: 2017-09-29T10:41:35.337143-05:
      DOI: 10.1002/adem.201700488
       
  • Understanding Wear Interface Evolution to Overcome Friction and Restrain
           Wear of TiAl–10 wt%Ag Composite
    • Authors: Kang Yang; Hongru Ma, Xiyao Liu, Qiang He
      Abstract: The main objective of this paper is to study wear interface evolution for analyzing the of friction and wear property of TiAl–10 wt%Ag composite. The results show that the friction coefficient and wear rate of TiAl–10 wt%Ag rapidly reduce at 0–25 min and rhythmically fluctuate at 25–60 min. TiAl–10 wt%Ag at 60–240 min obtains low friction and less wear. It is concluded that silver with the low shearing strength of about 125 MPa shows the eminent plastic deformation on wear interface. It effectively reduces friction resistance and material loss, cause TiAl–10 wt%Ag to obtain low friction coefficient, and less wear rate at 0–25 min. Increased silver content, reduces oxide content, and varies wear mechanisms cause the repeating variation of friction resistance and material loss, which results in the rhythmical fluctuation of friction coefficient and wear rate at 25–60 min. High silver contents exist on smooth wear interfaces, exhibit the eminent plastic deformation to lower friction and reduce wear. TiAl–10 wt%Ag obtains the low friction and less wear at 60–240 min.At 240 min, small plastic deformation body forms on smooth wear interface. It indicates that the main wear mechanism of TiAl–10 wt%Ag is plastic deformation. The FESEM surface micro-morphology of wear interface in rectangular region is clearly exhibited. Solid lubricant silver is uniformly distributed on wear interface, and exhibits excellent plastic deformation, leading to low friction and less wear.
      PubDate: 2017-09-28T11:27:37.882845-05:
      DOI: 10.1002/adem.201700637
       
  • Porous Polymer Membranes by Hard Templating – A Review
    • Authors: Mario Stucki; Michael Loepfe, Wendelin J. Stark
      Abstract: Membranes are designed to bridge a precise separation process at the nanoscale with industrial applications running at cubic meters per hour. This review outlines materials applied in membrane production with a particular focus on polymers. Membrane performance and created value are directly linked to controlled pore formation. Their economic relevance has created a number of large companies and associated academic research at top institutions. The authors review, therefore, starts from well-established techniques applied in products and then moves on to evolving concepts from academia. Pore formation through hard templating is a versatile field for separation processes. A more detailed view is given on the two known concepts for nanopore formation, namely colloidal templates and random hard salt templating. A comparison between these two concepts underlines their relevance to combine a process specific separation with large scale manufacturing requirements (i.e., upscale possibility, flexible process control and environmental impact).Membranes bridge nanoscale separation with high volume throughput. The development of membranes has resulted in a large variety of materials used for porous separators. This article introduces the relevant membrane processes and focuses on porous polymer membranes. Its main body explains sacrificial hard templating. Ordered colloidal crystals are compared to random templates with respect to their scalability and application.
      PubDate: 2017-09-28T00:05:53.544922-05:
      DOI: 10.1002/adem.201700611
       
  • A Combined Electromagnetic Levitation Melting, Counter-Gravity Casting,
           and Mold Preheating Furnace for Producing TiAl Alloy
    • Authors: Jieren Yang; Hu Wang, Yulun Wu, Xuyang Wang, Rui Hu
      Abstract: In this work, the authors describe the development of TiAl castings over a wide range of approaches. To overcome casting defects and cracks that appear in TiAl castings, a novel furnace is designed and constructed. The design combines induction skull melting, counter-gravity casting, and mold heating, which facilitates both filling and microstructure formation via a controllable process. This aim is to improve shaping capabilities and microstructural control for TiAl castings. Melting and casting experiments on TiAl alloys with a nominal composition corresponding to Ti–48Al–2Cr–2Nb (at%) are carried out and discussed. X-ray examinations indicate that the shaping of the TiAl components dose not contain macro casting defects, validating the advantages of this technique. The results are of interest to researchers devoted to technical innovations and modifications for TiAl casting at the industrial scale.The design combines induction skull melting, counter-gravity casting and mold heating a), which facilitates the shaping of the TiAl components b and c), and the decreasing of the defect d) via a controllable process. The results are of interest to researchers devoted to produce high-quality TiAl castings.
      PubDate: 2017-09-25T11:11:37.441471-05:
      DOI: 10.1002/adem.201700526
       
  • Tensile Strength Evolution and Damage Mechanisms of Al–Si Piston Alloy
           at Different Temperatures
    • Authors: Meng Wang; Jianchao Pang, Yu Qiu, Haiquan Liu, Shouxin Li, Zhefeng Zhang
      Abstract: The Al–Si piston alloys always bear different temperatures because of its peculiar component structure and service condition. Therefore, the tensile strength, elongation to fracture, and corresponding damage mechanisms of Al12SiCuNiMg piston alloys (ASPA) have been investigated with in situ technique at different temperatures. The tensile properties show two-stage tendencies: the former stage (25–280 °C) is determined by easily broken phases with inherent brittleness (such as primary Si), and the fracture behavior presents rapid brittle fracture after reaching the critical stress (about 430 MPa, based on in situ technique and the elastic stress field model). The later one (280–425 °C) is dominated by particles debonding and θphase coarsening. The plastic deformation behavior, dynamic recovery, and flow process become more significant on account of thermal activation. The Considère criterion h = K indicates that the transition of damage behaviors from insufficient local strength to insufficient matrix strength and the corresponding failure model shifts from brittle to ductile fracture. Based on the damage mechanisms, the elastic field model and thermal activation relation model have been established to characterize the strength of the ASPA at different temperature ranges.The tensile properties of Al-Si alloy show two-stage tendencies: the former stage is 25–280 °C and later one is 280–425 °C. Fracture mechanism changes from broken Si (insufficient local strength) at 25 °C to debonding particles (insufficient matrix strength) at 350 °C.The elastic field model and thermally activation relation model have been established to characterize the strength at different temperature ranges.
      PubDate: 2017-09-25T01:52:22.944493-05:
      DOI: 10.1002/adem.201700610
       
  • High-Entropy Alloy (HEA)-Coated Nanolattice Structures and Their
           Mechanical Properties
    • Authors: Libo Gao; Jian Song, Zengbao Jiao, Weibing Liao, Junhua Luan, James Utama Surjadi, Junyang Li, Hongti Zhang, Dong Sun, Chain Tsuan Liu, Yang Lu
      Abstract: Nanolattice structure fabricated by two-photon lithography (TPL) is a coupling of size-dependent mechanical properties at micro/nano-scale with structural geometry responses in wide applications of scalable micro/nano-manufacturing. In this work, three-dimensional (3D) polymeric nanolattices are initially fabricated using TPL, then conformably coated with an 80 nm thick high-entropy alloy (HEA) thin film (CoCrFeNiAl0.3) via physical vapor deposition (PVD). 3D atomic-probe tomography (APT) reveals the homogeneous element distribution in the synthesized HEA film deposited on the substrate. Mechanical properties of the obtained composite architectures are investigated via in situ scanning electron microscope (SEM) compression test, as well as finite element method (FEM) at the relevant length scales. The presented HEA-coated nanolattice encouragingly not only exhibits superior compressive specific strength of ≈0.032 MPa kg−1 m3 with density well below 1000 kg m−3, but also shows good compression ductility due to its composite nature. This concept of combining HEA with polymer lattice structures demonstrates the potential of fabricating novel architected metamaterials with tunable mechanical properties.High entropy alloy (HEA)-coated nanolattice structures with tunable mechanical properties have been developed, with the characteristics feature sizes spanning from 5 nm to 20 μm.
      PubDate: 2017-09-20T03:11:21.139452-05:
      DOI: 10.1002/adem.201700625
       
  • Nucleation Crystallography of Ni Grains on CrFeNb Inoculants Investigated
           by Edge-to-Edge Matching Model in an IN718 Superalloy
    • Authors: Wenchao Yang; Pengfei Qu, Lin Liu, Ziqi Jie, Taiwen Huang, Feng Wang, Jun Zhang
      Abstract: In this work, the nucleation crystallography of CrFeNb intermetallic particles as a grain refiner for Ni-based IN718 superalloys is studied using Edge-to-Edge Matching model. Three distinguishable orientation relationships between CrFeNb intermetallic particles and Ni grains are well predicted: [11¯0]Ni∖∖[1¯21¯0]CrFeNb, (111)Ni 1.28° from (0004)CrFeNb, [11¯0]Ni∖∖[1¯21¯0]CrFeNb, (111)Ni 1.32° from (202¯0)CrFeNb, and [11¯0]Ni//[0001]CrFeNb, (111)Ni 0.72° from (202¯0)CrFeNb. The results indicate that CrFeNb intermetallic particles have a strong nucleation potency as an effective grain refiner for Ni-based superalloy and the existence of semi-coherent interfaces between the CrFeNb intermetallic particles and Ni grains. Furthermore, the IN718 superalloy is used to experimentally validate the grain refinement effect of CrFeNb intermetallic particles, showing that its grain size is obviously refined from 8.60 to 1.23 mm. And, the corresponding heterogeneous nucleation mechanism of grain refinement at the atomic level is further identified.The nucleation crystallography of CrFeNb particle on Ni grain is studied using Edge-to-Edge Matching model. Three orientation relationships are predicted to indicate a semi-coherent interface. A relaxation of some atoms may be necessary to minimize the nucleation interface energy. IN718 superalloy is used to validate the grain refinement effect.
      PubDate: 2017-09-20T02:45:26.937527-05:
      DOI: 10.1002/adem.201700568
       
  • Mechanical Properties of a Novel Zero Poisson's Ratio Honeycomb
    • Authors: Yu Chen; Ming-Hui Fu
      Abstract: In this paper, a novel honeycomb is proposed by embedding a rib into every cell of the existing zero Poisson's ratio (ZPR) configuration, semi re-entrant honeycomb (SRH). Analytical model is developed to investigate the in-plane mechanical properties of the new honeycomb, and the resulting theoretical expressions are compared with the experimental tests and numerical results obtained from two different finite element (FE) models (3D beam model and 3D solid model), leading to a good correlation. FE analysis, analytical modeling, and experimental tests of the new honeycomb show that it can achieve ZPR effect in two principal directions. For further studies, parameters analyses are carried out to explore the dependence of the in-plane mechanical properties versus the geometric parameters. The results show that bending is the dominated deformation model when the new honeycomb is compressed along the x- direction, while stretch controlled in the y- directional compression. It is remarkable that the new proposed honeycomb features superior specific stiffness and more flexible in mechanical properties tailoring compared to the other ZPR honeycombs in the literature. Given these benefits, the new honeycomb may be promising in some practical applications.Honeycombs with zero Poisson's ratio (ZPR) are increasingly used in many important fields because of their unusual properties. A novel ZPR honeycomb is proposed by embedding a rib into every cell of the existing ZPR configuration, semi re-entrant honeycomb (SRH). The new proposed ZPR honeycomb exhibits superior specific stiffness and shows flexible in mechanical properties tailoring. Given these benefits, it may be promising in some applications.
      PubDate: 2017-09-19T01:20:37.058205-05:
      DOI: 10.1002/adem.201700452
       
  • ZnO Coated Anodic 1D TiO2 Nanotube Layers: Efficient Photo-Electrochemical
           and Gas Sensing Heterojunction
    • Authors: Siowwoon Ng; Petr Kuberský, Milos Krbal, Jan Prikryl, Viera Gärtnerová, Daniela Moravcová, Hanna Sopha, Raul Zazpe, Fong Kwong Yam, Aleš Jäger, Luděk Hromádko, Ludvík Beneš, Aleš Hamáček, Jan M. Macak
      Abstract: The authors demonstrate, in this work, a fascinating synergism of a high surface area heterojunction between TiO2 in the form of ordered 1D anodic nanotube layers of a high aspect ratio and ZnO coatings of different thicknesses, produced by atomic layer deposition. The ZnO coatings effectively passivate the defects within the TiO2 nanotube walls and significantly improve their charge carrier separation. Upon the ultraviolet and visible light irradiation, with an increase of the ZnO coating thickness from 0.19 to 19 nm and an increase of the external potential from 0.4–2 V, yields up to 8-fold enhancement of the photocurrent density. This enhancement translates into extremely high incident photon to current conversion efficiency of ≈95%, which is among the highest values reported in the literature for TiO2 based nanostructures. In addition, the photoactive region is expanded to a broader range close to the visible spectral region, compared to the uncoated nanotube layers. Synergistic effect arising from ZnO coated TiO2 nanotube layers also yields an improved ethanol sensing response, almost 11-fold compared to the uncoated nanotube layers. The design of the high-area 1D heterojunction, presented here, opens pathways for the light- and gas-assisted applications in photocatalysis, water splitting, sensors, and so on.Ultrathin and homogeneous ZnO coatings within high aspect ratio TiO2 nanotubular structure are demonstrated. ALD ZnO coatings within high surface area TiO2 nanotubes layer form a heterojunction with excellent photoelectrochemical activity and good ethanol sensing response. These enhancements are contributed by the passivated surface traps on tube wall, increased light absorption, close match of coating thickness, and Debye length.
      PubDate: 2017-09-19T01:20:26.109066-05:
      DOI: 10.1002/adem.201700589
       
  • Strategies for Drug Encapsulation and Controlled Delivery Based on
           Vapor-Phase Deposited Thin Films
    • Authors: Alberto Perrotta; Oliver Werzer, Anna Maria Coclite
      Abstract: Vapor-phase deposition methods allow the synthesis and engineering of organic and inorganic thin films, with high control on the chemical composition, physical properties, and conformality. In this review, the recent applications of vapor-phase deposition methods such as initiated chemical vapor deposition (iCVD), plasma enhanced chemical vapor deposition (PE-CVD), and atomic layer deposition (ALD), for the encapsulation of active pharmaceutical drugs are reported. The strategies and emergent routes for the application of vapor-deposited thin films on the drug controlled release and for the engineering of advanced release nanostructured devices are presented.Vapor-phase deposition methods allow the synthesis of (in)organic thin films, with high control on the chemical-physical properties and conformality. In this review, the encapsulation strategies of active drug molecules by means of vapor phase deposition processes are reported. The effects of (pre-) treatment and thin film deposition on controlled drug release and morphology are also reviewed, together with future perspectives and ‘smart’ device applications.
      PubDate: 2017-09-19T00:16:03.700173-05:
      DOI: 10.1002/adem.201700639
       
  • Sub-Micron Anisotropic InP-based III–V Semiconductor Material Deep
           Etching for On-Chip Laser Photonics Devices
    • Authors: Doris Keh-Ting Ng; Chee Wei Lee, Vivek Krishnamurthy, Qian Wang
      Abstract: Two InP-based III–V semiconductor etching recipes are presented for fabrication of on-chip laser photonic devices. Using inductively coupled plasma system with a methane free gas chemistry of chlorine and nitrogen at a high substrate temperature of 250 °C, high aspect ratio, anisotropic InP-based nano-structures are etched. Scanning electron microscopy images show vertical sidewall profile of 90° ± 3°, with aspect ratio as high as 10. Atomic Force microscopy measures a smooth sidewall roughness root-mean-square of 2.60 nm over a 3 × 3 μm scan area. The smallest feature size etched in this work is a nano-ring with inner diameter of 240 nm. The etching recipe and critical factors such as chamber pressure and the carrier plate effect are discussed. The second recipe is of low temperature (−10 °C) using Cl2 and BCl3 chemistry. This recipe is useful for etching large areas of III–V to reveal the underlying substrate. The availability of these two recipes has created a flexible III–V etching platform for fabrication of on-chip laser photonic devices. As an application example, anisotropic InP-based waveguides of 3 μm width are fabricated using the Cl2 and N2 etch recipe and waveguide loss of 4.5 dB mm−1 is obtained.Two InP-based III-V semiconductor etching recipes are presented for fabrication of on-chip laser photonic devices using inductively coupled plasma system with a methane free gas chemistry. The smallest feature size etched in this work is a nano-ring with inner diameter of 240 nm. InP-based waveguides of 3 μm width fabricated give a waveguide loss of 4.5 dB mm–1.
      PubDate: 2017-09-18T08:06:10.535529-05:
      DOI: 10.1002/adem.201700465
       
  • Multi-Stable Mechanical Structural Materials
    • Authors: Lingling Wu; Xiaoqing Xi, Bo Li, Ji Zhou
      Abstract: Energy absorbing is an important and desirable property in mechanical and civil engineering. Here, a proof-of-concept method is presented as a new approach to achieve artificial mechanical materials with tunable compressive behavior for energy absorbing constructed from unit cells with a snap fit structure. The artificial structure undergoes a series of stable configurations derived from the sequential insertion of the plug into the groove of the snap fit. Both, experimental and simulation results manifest the multi-stable and tunable mechanical properties of the structure. The mechanical energy dissipated by the proposed structure is demonstrated to be dependent on the lead-in angle of the snap fit and the deflection ratio of the groove, as well as on the coefficient of friction between the plug and the groove of the snap fit. The system designed, herein, exhibits mechanical properties that can be tuned not only by adjusting the geometric parameters, but also by tuning the coefficient of friction between the plug and the groove, allowing the mechanical properties to be tailored post-fabrication. Furthermore, the proposed model can be extended to the macro-, micro-, or nanoscales. These findings provide a simple method to obtain artificial materials with tunable energy absorbing properties, which can be applied in areas such as the design of automobile bumpers and foldable devices that facilitate their transportation.In this paper, the authors proposed a new class of mechanical structural material with multi-stable mechanical properties for energy absorbing and demonstrated its fabrication using Sylgard® 184 silicone. The proposed model is constructed from unit cells having a snap fit structure, which has two stable configurations derived from the insertion of the plug into the groove of the snap fit. During the deformation, the tilting beams store a portion of energy, while the remaining energy is dissipated by the mechanical friction effect between the plug and groove of the snap fit. Besides, the energy absorbed (E_in) and the energy required to break the second equilibrium state (E_out) can be tuned independently. The relationships between the mechanical performance and the geometric parameters of the snap fit are investigated via both simulations and experiments. Adjustable energy absorption properties are obtained by changing the width ratio, the lead-in angle, and the coefficient of friction of the snap fit, which permits a more practicable method to tune the mechanical properties of the structural material. The mechanism proposed, herein, is theoretically scale-independent, that is, the manipulation of the mechanical properties can be extended to the micro- or nanoscale, if appropriate fabrication processes are available. This approach proves to be a low-cost, easily accessible, and reusable method that has a broad application potential in industry, such as in the design of automobile bumper beams, vibration isolation materials, and foldable instruments.
      PubDate: 2017-09-18T08:05:45.553865-05:
      DOI: 10.1002/adem.201700599
       
  • Antibacterial Efficacy of Sacrifical Anode Thin Films Combining Silver
           with Platinum Group Elements within a Bacteria-Containing Human Plasma
           Clot
    • Authors: Adham Abuayyash; Nadine Ziegler, Jan Gessmann, Christina Sengstock, Thomas A. Schildhauer, Alfred Ludwig, Manfred Köller
      Abstract: Silver (Ag) dots arrays (64 and 400 dots per mm2) are fabricated on a continuous platinum (Pt), palladium (Pd), or iridium (Ir) thin film (sacrifical anode systems for Ag) and for comparison on titanium (Ti) film (non-sacrifical anode system for Ag) by sputter deposition and photolithographic patterning. The samples are embedded within a tissue-like plasma clot matrix containing Staphylococcus aureus (S. aureus), cultivated for 24 h. Bacterial growth is analyzed by fluorescence microscopy. Among platinum group sacrifical anode elements and a dense Ag sample, only the high Ag ion releasing Ag–Ir system is able to inhibit the bacterial growth within the adjacent plasma clot matrix. This study demonstrates that the antibacterial efficiency of Ag coatings is reduced under tissue-like conditions. However, the new sacrificial anode based Ag–Ir system can overcome this limitation.Sacrificial anode silver dot arrays, fabricated on continuous platinum, palladium, or iridium thin films by sputter deposition and photolithographic patterning are embedded within a tissue-like plasma clot matrix containing growing Staphylococcus aureus. Among these samples or a dense Ag film, only the Ag–Ir dot array is able to inhibit the bacterial growth within the plasma clot matrix.
      PubDate: 2017-09-18T08:00:22.123943-05:
      DOI: 10.1002/adem.201700493
       
  • Effect of Thermal Oxidation on Microstructure and Corrosion Behavior of
           the PVD Hf-Coated Mg Alloy
    • Authors: Dongfang Zhang; Zhengbing Qi, Binbin Wei, Zhoucheng Wang
      Abstract: Hafnium coatings are fabricated on magnesium alloys by magnetron sputtering and are further submitted to the thermal oxidation treatment at temperature of 200, 300, and 400 °C. The thin hafnium oxide film and new grain boundaries are observed on the hafnium coatings during the appropriate treatment temperature (300 °C). These changes in microstructure result in surface densification, oxidation, and low porosity of the treated coating that significantly decrease its susceptibility to corrosion. Consequently, the thermal oxidation treatment hafnium coating exhibits a more positive corrosion potential, lower corrosion current density, and higher polarization resistance than that of the as-deposited coating using an electrochemical system. Moreover, the enhanced adhesion of the treated coating produced by applying an appropriate treatment temperature facilitates an efficient long-term protection of magnesium alloy.Thermal oxidation as an effective yet feasible post-treatment is conducting on the PVD Hf coated Mg alloy. Surface densification, thin oxide film, and enhanced adhesion are obtained on the post treated coating. As a result, the treated coating exhibits more efficient barrier to corrosive media with positive corrosion potential, low corrosion current density, and high polarization resistance.
      PubDate: 2017-09-18T01:00:38.093829-05:
      DOI: 10.1002/adem.201700556
       
  • MWCNTs as Conductive Network for Monodispersed Fe3O4 Nanoparticles to
           Enhance the Wave Absorption Performances
    • Authors: Kaili Yu; Min Zeng, Yichao Yin, Xiaojun Zeng, Jue Liu, Ya Li, Wukui Tang, Yu Wang, Jing An, Jun He, Ronghai Yu
      Abstract: Magnetic oxides are widely used as electromagnetic (EM) wave absorbers. To promote the absorption efficiency, tremendous efforts have been contributed to adjusting the composite, structure, and size of magnetic loss materials. Employing carbon materials (CNTs, CF, graphene, PANI) is an efficient way to improve the dielectric loss of the matrix. Anchoring the tiny-monodispersed Fe3O4 nanoparticles (NPs) onto the lightweight multi − walled carbon nanotubes (MWCNTs) leads to improve dielectric loss and impedance matching characteristic. Magnetic Fe3O4 NPs along the one-dimensional nanotubes direction play a good synergetic role with MWCNTs due to the interfacial strong chemical and structure bonding. The as-synthesized Fe3O4/MWCNTs nanocomposites exhibit efficient EM wave absorption characteristics (RL av−10 dB) with a maximum reflection loss of −63.64 dB at 12.08 GHz and a diminutive thickness of only 1.6 mm. The magnetic Fe3O4 NPs show strong chemical and structure bonding with the one-dimensional MWCNTs. This work may show a way to broaden the application of such kinds of lightweight high-performance absorbing materials frameworks.Anchoring the tiny and monodispersed Fe3O4 NPs onto the lightweight MWCNTs results in a strong bonding in Fe3O4/MWCNTs nanocomposites, which exhibit excellent EM wave absorption properties. The MWCNTs can act as the conductive network to enhance the dielectric loss and balance the magnetic loss for good impedance matching.
      PubDate: 2017-09-18T01:00:29.878778-05:
      DOI: 10.1002/adem.201700543
       
  • Graphene Oxide/Polymer-Based Biomaterials
    • Authors: Duygu Ege; Ali Reza Kamali, Aldo R. Boccaccini
      Abstract: Since its discovery in 2004, derivatives of graphene have been developed and heavily investigated in the field of tissue engineering. Among the most extensively studied forms of graphene, graphene oxide (GO), and GO/polymer-based nanocomposites have attracted great attention in various forms such as films, 3D porous scaffolds, electrospun mats, hydrogels, and nacre-like structures. In this review, the most actively investigated GO/polymer nanocomposites are presented and discussed, these nanocomposites are based on chitosan, cellulose, starch, alginate, gellan gum, poly(vinyl alcohol) (PVA), poly(acrylamide), poly(ϵ-caprolactone) (PCL), poly(lactic acid) (PLLA), poly(lactide-co-glycolide) (PLGA), gelatin, collagen, and silk fibroin (SF). The biological and mechanical performance of such nanocomposites are comprehensively scrutinized and ongoing research questions are addressed. The analysis of the literature reveals overall the great potential of GO/polymer nanocomposites in tissue engineering strategies and indicates also a series of challenges requiring further research efforts.In this review paper, the mechanical and biological performance of graphene oxide/polymeric nanocomposites are analyzed in detail and discussed. Additionally, useful graphics are provided which lead researchers to compare the mechanical properties of films, electrospun mats, fibers, nacre-like structures, and hydrogels of graphene oxide/polymeric nanocomposites at first glance. Finally, the potential of these nanocomposites in tissue engineering are reported with suggestions for future research.
      PubDate: 2017-09-14T07:41:13.801311-05:
      DOI: 10.1002/adem.201700627
       
  • Hydrogen Trapping in Some Automotive Martensitic Advanced High-Strength
           Steels
    • Authors: Jeffrey Venezuela; Qingjun Zhou, Qinglong Liu, Mingxing Zhang, Andrej Atrens
      Abstract: Hydrogen permeation experiments are used to investigate hydrogen trapping in commercial automotive martensitic advanced high-strength steels. Hydrogen trapping increases with increasing mechanical strength, as indicated by (i) the decrease in the hydrogen diffusion coefficient, and (ii) the increase in reversible hydrogen trap density. The measured trap densities are in the order of ≈1017– ≈ 1018 cm−3. The relationship between trapping characteristics and HE susceptibility of MS-AHSS is discussed in terms of Hydrogen Enhanced Macroscopic Plasticity (HEMP) and Hydrogen Assisted Micro-fracture (HAM).Reversible trapping of hydrogen by dislocations may explain the hydrogen-influenced behavior in the MS-AHSS: (i) the reduction of the yield strength by the Hydrogen Enhanced Macroscopic Plasticity (HELP) mechanism, and (ii) the occurrence of shear micro-fracture by the Hydrogen Assisted Micro-fracture (HAM) mechanism.
      PubDate: 2017-09-13T13:02:10.393178-05:
      DOI: 10.1002/adem.201700468
       
  • Reticulated Replica Ceramic Foams: Processing, Functionalization, and
           Characterization
    • Authors: Tobias Fey; Ulf Betke, Stefan Rannabauer, Michael Scheffler
      Abstract: Reticulated ceramic foams are used in a wide range of applications such as filters, catalyst supports, lightweight materials, energy absorptions materials, or as scaffolds for tissue engineering as the most common ones. Based on gaseous foaming processes of polymers, a stochastic distribution of closed pores is obtained. By reticulation processing thin foam windows are removed between cells turning a closed cell into an open cell structure. These foams are used as template for porous ceramics manufacturing: With different processing approaches, for example, with dip coating of a ceramic slurry and a subsequent (multistep) thermal treatment ceramic reticulate foams are obtained. A variety of material properties strongly depend on the cell and strut size, as well on material composition. Functionalization of ceramic foam surfaces (outer surface functionalization), for example, with zeolites or nanosized aggregates lead to an increase of the specific surface area or provides catalytic or heat storage functionality. Filling of struts (inner surface functionalization) may lead to improved mechanical stability or may provide functionalities such as electric conductivity. The present work summarizes the processing steps from the template foam to the final cellular ceramic, functionalization strategies, and the most common characterization techniques.This paper reviews reticulated porous ceramics resulting from a manufacturing process described first in 1963. The focus is set to processing parameters, slurry rheology, and porperties to modification strategies and to characterization methods of foam properties. It may help the readers to identify future research potential.
      PubDate: 2017-09-04T05:35:36.763837-05:
      DOI: 10.1002/adem.201700369
       
  • Tailored Surface Properties of Ceramic Foams for Liquid Multiphase
           Reactions
    • Authors: Katja Schelm; Michael Schwidder, Janis Samuel, Franziska Scheffler, Michael Scheffler
      Abstract: Open cellular ceramic foams are prepared using the replica method. In a second step, these foams are coated with a pre-ceramic or polymer-derived ceramic coating, respectively. Polymer-to-ceramic transformation is studied by SEM with respect to the microstructure, functional groups are characterized by Raman microscopy, density and porosity are determined by pycnometer measurements as well as the surface free energy by means of contact angle measurements. By pyrolysis at different temperatures between 403 and 1273 K, the surface wettability is adjusted in a wide range from hydrophilic to hydrophobic due to the release of organic groups from the pre-ceramic polymers in terms of polymer-to-ceramic transformation. Coated foams are tested in a new potential application: as reactor internals to increase the liquid–liquid interface area in a homogeneously catalyzed multiphase system. As model reaction, a reactive extraction of an organic dye was used and the influence of the surface energy of the foam on the phase dispersion/reaction rate is discussed. The coated foams are able to increase the reaction rate to an extent depending on the surface wettability.Ceramic foams are prepared and coated with pre-ceramic polymers. These coating offers to tailor the surface properties like the wetting behavior in wide range by variation of the pyrolysis temperature. Due to the foams structure, they are useful for novel multi-phase mixing processes. This work shows the dependence of the phase dispersion of two immiscible liquid phases. This work shows the dependence of the phase dispersion of two immiscible liquid phases on the surface wettability of the foams.
      PubDate: 2017-07-21T06:45:28.600191-05:
      DOI: 10.1002/adem.201700418
       
  • Influence of Cell Size on Mechanical and Piezoelectric Properties of PZT
           and LNKN Ceramic Foams
    • Authors: Franziska Eichhorn; Jonas Biggemann, Simone Kellermann, Akinobu Kawai, Kensuke Kato, Kenichi Kakimoto, Tobias Fey
      Abstract: Piezoceramic foams made of lead zirconate titanate (PZT) and lithium sodium potassium niobate (LNKN-6) containing an open porosity>75 vol% are manufactured with varying cell size from 1369 to 265 μm and accordingly, strut size from 346 to 46 μm by replica method. Pore size distribution and strut thickness are determined by X-ray micro tomography investigations of PZT foams with 10, 30, 45, and 80 pores per inch (ppi). Fracture strengths σb between 0.29 and 1.52 MPa (PZT) and 0.04 and 0.07 MPa (LNKN-6) are determined by compression test and compared to Gibson and Ashby's model of open- and closed-cell foams and in dependence of the cell size. The longitudinal and transversal coupling coefficients d33 and d31 decrease in a range of 38 to 178 pCN−1 or −13 to −100 pCN−1 compare to dense reference material. In dependence of the cell size, the values of the coupling coefficients change about 79–93%. The relative permittivity decreases 93% by decreasing the cell size of the PZT and LNKN-6 foams.Piezoceramic foams of PZT and LNKN-6 (porosity>75 vol%) are manufactured by replica method. Depending on the cell size fracture strengths σb varied between 0.29 and 1.52 MPa (PZT) and 0.04 and 0.07 MPa (LNKN-6), as well the longitudinal and transversal coupling coefficients d33 and d31 decreased in a range of 38 to 178 pCN−1 or −13 to −100 pCN−1.
      PubDate: 2017-07-07T02:16:30.350748-05:
      DOI: 10.1002/adem.201700420
       
  • Open-Porous Silicon Nitride-Based Ceramics in Tubular Geometry Obtained by
           Slip-Casting and Gelcasting
    • Authors: Dominik Brouczek; Thomas Konegger
      Abstract: Owing to its unique properties, silicon nitride is a frequently used materials choice in highly demanding applications in terms of thermal and mechanical load. In this work, porous silicon nitride-based support materials in hollow-tube configuration are generated through colloidal forming, and their respective properties for potential applications in the fields of membrane-based separation, filtration, or catalysis are evaluated. Shaping of the ceramics is achieved by two distinct casting techniques, slip-casting, and gelcasting, and the results of the respective methods are set in relation. Furthermore, a special focus is set on the correlation between sintering parameters and resulting porosity. Subsequently, air permeabilities of the generated structures are determined, illustrating a direct relation between processing parameters and resulting permeability. Darcian permeability values of up to 9 · 10−16 m2 are observed for samples exhibiting total porosities between 32 and 41 %. The findings allow for a predictability of suitable permeation properties for the structures’ anticipated application as complex-shaped non-oxide ceramic supports for membrane-based separation or catalysis, or as high-performance filter materials.Two distinct colloidal-based casting approaches (slip-casting and gelcasting) are evaluated for the generation of porous Si3N4 ceramics in tubular geometry, suitable for prospective applications in the fields of separation or catalysis. Partial sintering facilitates tightly controllable pore morphologies, thus allowing for a direct correlation between processing, porosity, and permeability characteristics of the tubular structures prepared.
      PubDate: 2017-07-03T01:20:37.057617-05:
      DOI: 10.1002/adem.201700434
       
  • Increased Mechanical Stability and Thermal Conductivity of Alumina
           
    • Authors: Stefan Rannabauer; Gerrit-Maximilian Söffker, Marcel Scheunemann, Ulf Betke, Michael Scheffler
      Abstract: Infiltration processing of reticulated porous alumina ceramics (RPC) from reticulated foam manufacturing is investigated by micro computed tomography. Infiltration is carried out with colloidal alumina slurries. Successful infiltration is found to be a function of the RPCs starting microstructure and the particle size of the alumina in the colloidal infiltration system. Suitable infiltration conditions are specified. As a result, RPCs with a low relative density show a fivefold compressive strength after infiltration, as compared to their non-infiltrated RPC counterparts. The highest strength of infiltration processed alumina RPCs at a porosity of 90% is found to be 1.6 MPa, and besides a significant increase of the compressive strength, the thermal conductivity is improved to be 1.5 W m−1 K−1 after infiltration.Infiltration of RPC with colloidal alumina slurries is investigated with respect to the colloidal particle size. Classifying the RPCs’ pore system into different pore orders, the distribution of the colloidal particles is examined by micro computed tomography. The infiltration results in a significant improvement of the struts and thereby the RPC.
      PubDate: 2017-06-09T07:35:27.227864-05:
      DOI: 10.1002/adem.201700211
       
  • Investigations of Corrosion Resistance of Laser Separated Open Cell
           Metal 
    • Authors: Robert Baumann; Patrick Herwig, Andreas Wetzig, Eckhard Beyer
      Abstract: Open cell metal foam contributes promising solutions to the light weight design, battery applications, and renewable energy. Still, challenges are present concerning the cutting into a defined shape. Mechanical processes like milling and grinding create surface smearing on the foam, which leads to a loss of their open cell behavior. Laser remote cutting offers a promising solution in order to overcome those challenges. Their investigations consider that this technique has a high potential concerning cutting speed, which is increased by more than 500% compared to state of the art laser separation techniques. Nevertheless, quality improvements regarding spatter formation and fouling or corrosion resistance has to be investigated. This paper offers insight into the viability of remote laser cutting and how quality aspects can be improved.Remote laser cutting offers cut velocities up to 300 m min–1 for open cell metal foam. Note, that the open cell character is still present after machining. In their investigations, salt spray test and alternating climate changing are executed. The laser influences areas exhibit less corrosion behavior. Remote laser cutting shows the best way for sizing open cell metal foams.
      PubDate: 2017-05-30T13:52:23.651528-05:
      DOI: 10.1002/adem.201700107
       
  • Manufacturing and Characterization of Highly Porous Bioactive Glass
           Composite Scaffolds Using Unidirectional Freeze Casting 
    • Authors: Laura M. Henning; Sara Zavareh, Paul H. Kamm, Miriam Höner, Horst Fischer, John Banhart, Franziska Schmidt, Aleksander Gurlo
      Abstract: The aim of this work is the fabrication of bioactive and degradable scaffolds for bone tissue engineering. Freeze casting is used to obtain macropores. Alongside, highly bioactive 45S5 Bioglass, gelatin and chitosan are used as biocompatible binder and stabilizing agent, respectively. By varying the cooling rate between 2 and 4 K min−1 and whether the slurry is allowed to form a gelled network at 7 °C before freeze casting or not, samples with a porosity of 75% are achieved. X-ray tomography analysis shows smallest pore sizes between 73 and 77 µm and a rather lamellar structure parallel to the freezing direction for the non-gelled samples, whereas the gelled samples have smallest pores between 96 and 120 µm and show a rather cellular structure. Compression tests reveal compressive strengths from 2 (non-gelled) to 3 MPa (gelled), while the quasielastic moduli of the gelled samples (44–46 MPa) clearly exceed values of the non-gelled (20–23 MPa). Thus, it is concluded that the modified pore structure caused by the gelling process markedly improves the mechanical properties of the samples. After seven days in SBF under physiological conditions, a calcium phosphate rich layer is detected on the samples surface, revealing the bioactivity of the scaffolds.The combination of gel casting and freeze casting results in better mechanical properties compared to the sole use of the conventional freeze casting technique. Highly porous 45S5 Bioglass/gelatin/chitosan composite scaffolds, which are gel casted before freeze casting, show an increase in the quasielastic moduli by 100% and potentially sufficient pore sizes for applications in bone tissue engineering.
      PubDate: 2017-05-29T04:31:14.910719-05:
      DOI: 10.1002/adem.201700129
       
  • Sandwich Structures Consisting of Aluminum Foam Core and Fiber Reinforced
           Plastic Top Layers 
    • Authors: Claudia Drebenstedt; Susi Rybandt, Welf-Guntram Drossel, Maik Trautmann, Guntram Wagner
      Abstract: Thinking of new approaches for light weight design with sandwiches, the combination of aluminum foam as core and fiber reinforced plastics as top layers can be a good way to increase the light weight aspect and combine advantages of both materials. For structural applications, often a high bending stiffness and a good damping capability in the combination with the lightweight aspect are needed. For these new sandwiches, especially, the bonding properties are crucial for later applications. Therefore, investigations regarding the bonding properties of the combination of the two components are carried out. The objective is to find a way of combining these materials without adhesives. Different ways of composite manufacturing are tested and compared according to DIN 53292: “testing of sandwiches; tensile test perpendicular to the faces”. Furthermore, different pretreatments of the foam core are compared. These include sandblasting with a chemically modified blasting material, a structure included by a modification of the foaming tool, and untreated foam for comparison reasons to the state of the art. It is found that the structure induced during the foaming step is suitable for adhesive bonding, but not for the other processes. Better results can be expected by further adaption of the implemented structure. The best results in the compression molding process are obtained with the sandblasted foam cores.Aluminum as core and fiber reinforced thermoplastic top layers are combined by compression molding to a new sandwich structure without additional adhesives. Evaluations by tensile tests regarding the bonding depending on the surface pretreatments are conducted. Finally, a demonstrator is realized.
      PubDate: 2017-05-23T04:05:57.298217-05:
      DOI: 10.1002/adem.201700066
       
  • On the Indentation Resistance of a PC Layer on PVC Foam Substrate 
    • Authors: Adam M. Boyce; Vikram S. Deshpande, Norman A. Fleck
      Abstract: The indentation response of a polycarbonate face sheet bonded to a PVC foam substrate is investigated experimentally and numerically. The deformation mode involves foam crushing, and membrane stretching of the PC layer at large indenter displacements; this is quantified using optical strain measurement techniques. The bottom corners of the foam substrate lifts off its underlying support when the foam layer is sufficiently thin. Peak load is dictated by tensile failure of the foam on the bottom face. Finite element simulations suggest that a deep foam core prevents this lift-off and results in a greater load carrying and energy absorption capacity.The indentation response of a polycarbonate face sheet bonded to a PVC foam substrate is investigated experimentally and numerically. The deformation mode involves foam crushing, and membrane stretching of the PC layer at large indenter displacements; this is quantified using optical strain measurement techniques. The bottom corners of the foam substrate lifts off its underlying support when the foam layer is sufficiently thin. A deep foam core prevents this lift-off and results in a greater load carrying and energy absorption capacity.
      PubDate: 2017-05-22T06:00:30.223866-05:
      DOI: 10.1002/adem.201700075
       
  • Novel Composite Foam Concept for Head Protection in Oblique Impacts 
    • Authors: Yasmine Mosleh; Jos Vander Sloten, Bart Depreitere, Jan Ivens
      Abstract: Rotational acceleration experienced by the head during oblique impacts is known to cause traumatic brain injuries. It is hypothesized that shear properties of a foam layer, used for head protection (e.g., protective helmet liners, headliners in cars) can be related to the extent of rotational acceleration transmitted to the head. Furthermore, it is hypothesized that by introducing anisotropy in a foam layer, rotational acceleration can be mitigated. In this study, an anisotropic composite foam concept is proposed to mitigate head rotational acceleration, hence reducing the risk of traumatic brain injuries. The composite foam concept introduces anisotropy in a foam at the “macro level”, combining different densities of foam in layered and quasi-fiber/matrix configurations. The performance of expanded polystyrene (EPS) composite foams in quasi-static compression and combined shear-compression loading and also linear and oblique impact experiments, has been compared with the performance of single layer EPS foam of similar thickness and density. The results of oblique head impact have been analyzed by global head injury criteria such as HIC, HICrot, and HIP. The composite foam concept demonstrates a great potential to be utilized in applications such as protective helmets due to the significant mitigation of brain injury risk.In this study, an anisotropic composite foam concept is proposed to mitigate head rotational acceleration, hence reducing the risk of traumatic brain injuries in oblique impacts. The composite foam concept introduces anisotropy in a foam at the “macro level,” combining different densities of foam in layered and quasi-fiber/matrix configurations. This concept can be used, for example, for helmets with complex shapes.
      PubDate: 2017-05-19T06:10:37.998045-05:
      DOI: 10.1002/adem.201700059
       
  • Impact of Slurry Composition on Properties of Cellular Alumina: A Computed
           Tomographic Study 
    • Authors: Ulf Betke; Sebastian Dalicho, Stefan Rannabauer, Alexandra Lieb, Franziska Scheffler, Michael Scheffler
      Abstract: Fine-pored, 45 ppi (pores per linear inch) alumina foams are prepared from ceramic slurries with varying contents of additives (deflocculant, binder) and solid loading following a standardized procedure. Rheological key parameters (yield stress, high-shear viscosity) of the respective slurries are determined by approximation of the experimental flow curves with appropriate rheological models. The resulting ceramic foams are characterized by computed tomography (CT) followed by a morphometric analysis of the reconstruction volume data. The main scope of the work involves the development of a procedure to reliably define the binarization threshold during these morphometric calculations, which is based on the analysis of the differential course of the total porosity results from calculations performed at varying binarization threshold values (“differential thresholding”). A very good match of the CT porosity results with experimental data is achieved, despite the unfavorable CT voxel resolution to foam structure fineness relation. The CT evaluation results are finally correlated to the rheological properties of the respective slurries used in foam manufacturing. The dominant slurry composition parameters are the weight fraction of the ceramic powder and the binder concentration. Increasing binder and solid content result in an increased yield stress and viscosity of the respective dispersion and consequently in a decreased porosity and cell size of the finally manufactured cellular ceramic.Fine-pored, 45 ppi alumina ceramic foams are prepared by the Schwartzwalder method from the respective ceramic dispersions. For these, the slurry composition is varied and its influence on the rheological parameters is investigated. The resulting foams are characterized by micro computed tomography including a new approach for the void  material segmentation. Finally, the µ-CT results are correlated to the rheological parameters of the slurries used in foam preparation.
      PubDate: 2017-05-17T08:40:28.317666-05:
      DOI: 10.1002/adem.201700138
       
  • Impact Testing of Polymer-filled Auxetics Using Split Hopkinson Pressure
           Bar 
    • Authors: Tomáš Fíla; Petr Zlámal, Ondřej Jiroušek, Jan Falta, Petr Koudelka, Daniel Kytýř, Tomáš Doktor, Jaroslav Valach
      Abstract: In this paper, impact testing of auxetic structures filled with strain rate sensitive material is presented. Two dimensional missing rib, 2D re-entrant honeycomb, and 3D re-entrant honeycomb lattices are investigated. Structures are divided into three groups according to type of filling: no filling, low expansion polyurethane foam, and ordnance gelatine. Samples from each group are tested under quasi-static loading and dynamic compression using Split Hopkinson Pressure Bar. Digital image correlation is used for assessment of in-plane displacement and strain fields. Ratios between quasi-static and dynamic results for plateau stresses and specific energy absorption in the plateau are calculated. It is found out that not only the manufactured structures, but also the wrought material exhibit strain rate dependent properties. Evaluation of influence of filling on mechanical properties shows that polyurethane increases specific absorbed energy by a factor of 1.05–1.4, whereas the effect of gelatine leads to increase of only 5–10%. Analysis of the Poisson's function reveals influence of filling on achievable (negative) values of Poisson's ratio, when compared to unfilled specimens. The results for the Poisson's function yielded apparently different values as the assessed minima of quasi-static Poisson's ratio in small deformations are constrained by a factor of 15.In this paper, additively manufactured auxetic lattices are subjected to impact loading using Split Hopkinson Pressure Bar (SHPB). Selected samples are filled with strain rate sensitive material. Digital image correlation is used for analysis of the deformation behavior of the samples. Influence of filling on the samples’ stress–strain curves, negative Poisson's ratio, and strain-rate sensitivity is investigated.
      PubDate: 2017-05-08T07:05:29.137599-05:
      DOI: 10.1002/adem.201700076
       
  • Mechanical Behavior of Particulate Aluminium-Epoxy Hybrid Foams Based on
           Cold-Setting Polymers 
    • Authors: Jörg Weise; André Felipe Queiroz Barbosa, Olga Yezerska, Dirk Lehmhus, Joachim Baumeister
      Abstract: New types of hybrid foams with cold-setting polymer foam matrix have been developed. These are based on AlSi10 foam granules and a cold-setting epoxy polymer foam phase. The mechanical characteristics of the hybrid foams like stiffness, compressive, and tensile strength were determined using quasi-static compression and tensile tests. Their overall mechanical behavior is compared to APM-(Advanced Pore Morphology)-based hybrid foams comprising similar aluminium foam granules in combination with single component hot setting epoxy foams. While the latter generally outperform the cold-setting variants at their present state of development, the ease of manufacturing in conjunction with promising levels of strength, and stiffness will support future application of the new material.Hybrid foam consisting of aluminium foam and cold-setting epoxy polymer foam can be used for the filling and reinforcement of hollow structures. While FoaminalTM aluminium foam outperforms the hybrid foam, the ease of manufacturing and promising level of strength and stiffness support future application of the new material.
      PubDate: 2017-05-08T01:29:38.371487-05:
      DOI: 10.1002/adem.201700090
       
  • Numerical and Experimental Investigations on the Growth of the
           Intermetallic Mg2Si Phase in Mg Infiltrated Si-Foams 
    • Authors: Fei Wang; Alexander M. Matz, Oleg Tschukin, Johann Heimann, Bettina S. Mocker, Britta Nestler, Norbert Jost
      Abstract: The present work explores the growing behavior of the intermetallic layer in the Mg-Si system. Following achievements have been obtained in our investigation: (i) A complete wetting concept is proposed for the lateral spreading of the intermetallic layer. (ii) In contrast to the stoichiometric property for the intermetallic phase in the phase diagram, the authors show that concentration gradients are able to be established in the kinetic process. (iii) Contrary to the reported growth behavior, d ∝ t0.25–0.5 in other intermetallics, the authors find a transition from d ∝ t to d ∝ t with an increase of the temperature, where d is the thickness of the intermetallic layer and t is the time.The growth of the intermetallic Mg2Si layer in the Mg infiltrated Si-foam is investigated. The formation of the intermetallic layer in the earlier stage is attributed to a complete wetting effect. With time, the thickness of the intermetallic phase d increases. Depending on whether the process is reaction, bulk diffusion, or grain boundary diffusion dominated, the authors have different growth behaviors: d ∝ t, d t, or d ∝ t1/3.
      PubDate: 2017-04-19T05:00:36.907525-05:
      DOI: 10.1002/adem.201700063
       
  • Optimization of a Cellular Glass Ceramic Produced from Water
           Potabilization Sludge for Structural and Chemical Applications 
    • Authors: Rosa María Ramírez Zamora; Fabricio Espejel Ayala, Iván Emilio MartínezHerrera, Víctor Manuel Sánchez Orendain, Gabriela Díaz, Myriam Solís López López, Rafael Schouwenaars
      Abstract: Waste sludge generated in the potabilization of surface water is used to produce cellular materials by mixing with clay and firing at 1 250 °C. An iron-rich glassy matrix with crystals of mullite and albite is formed. Porosity is generated by the slow release of H2O, which originates from the dehydroxilation of lepidocrocite at high temperature. The sludge/clay ratio and the sludge granulometry determine the properties of the product: from highly porous cellular foams to denser materials with high strength. Laboratory tests for both kinds of products show that the latter can be used as aggregates for low-density structural concrete. The former serve as a support material for the catalytic reduction of NOx in exhaust gases. Deposition conditions for Fe- and Pt-nanoparticles are optimized by experimental design, resulting in NOx-conversion rates close to 100%.The technical feasibility of using cellular ceramics produced from waste sludge is demonstrated for high-strength as well as high-porosity variants of this material, which consists of a glassy matrix with crystalline inclusions. At short firing times, the fine-grained fraction of the sludge produces a product suitable as an aggregate for lightweight structural concrete. The coarse grained fraction, at longer firing times, allows producing a permeable ceramic foam for catalyst support in selective reduction of NOx. The Pt and Fe-based catalysts tested are found to provide very high conversion rates even at high space velocities in an experimental reactor.
      PubDate: 2017-04-19T04:57:23.447507-05:
      DOI: 10.1002/adem.201700074
       
  • Analysis of Geometrical and Process-Related Parameters on the Impregnation
           Quality of Advanced Cellular Composites 
    • Authors: Oliver Weißenborn; Sirko Geller, Maik Gude
      Abstract: Based on the well-established polyurethane (PUR) spray coat method, an integral manufacturing process is developed to simultaneously create textile-reinforced top and bottom layers as well as the cellular core in one single production step for advanced sandwich structures. Since the foaming matrix impregnates the textile layers during expansion and also serves as core material in the final part, these sandwich elements are connected cohesively with each other. Within this paper, impregnation studies are conducted to evaluate the influence of process parameters, such as mold temperature and dwelling time of the foam matrix, as well as part geometry and foam density on the local yarn impregnation. Evaluation of cell morphology is performed by measuring the cell size distribution inside impregnated yarns.Novel processing technologies for smart design concepts of structural lightweight parts are of high relevance for industrial applications. In this context, the PUR spray coat method is used to impregnate carbon fiber textiles with a cellular matrix material by using the expansion reaction of PUR rigid foams. The influence on the local impregnation quality and composite morphology is investigated comprehensively.
      PubDate: 2017-04-10T06:21:31.810797-05:
      DOI: 10.1002/adem.201700087
       
  • Effects of Void Array Orientation on Compressive Properties of Cellular
           Structures 
    • Authors: Karl Laurence Dahm; Peter Norman McGavin, Ian Willian Murray Brown
      Abstract: Additively manufactured cellular materials enable customized structural implants with superior osseointegration potential and mechanical properties better matched to bone. In this investigation, the compression response of Ti–6Al–4V alloy cellular materials comprising a simple cubic array of 2.00 mm diameter spherical voids with a 1.90 mm inter-void spacing are studied. Finite element analysis (FEA) shows that the lattice exhibited cubic symmetry with values for Young's modulus (E), Poisson's ratio, and shear modulus in the range of 28.5–29.5 GPa, 0.18–0.20, and 5.4–6.0 GPa, respectively. Compression tests carried out on cylinders with the same cellular structure fabricated by selective laser melting also show a strong dependence of elastic and plastic properties on orientation. Compression normal to the {100} plane of the simple cubic cell gives the highest E and strength, while compression normal to the {110} and {111} planes give lower values. The experimental E values for the {100} and {111} orientations show good agreement with the FEA results, but the {110} orientation shows lower values of E compared to the FEA predictions. Ultimate compressive failure of the cylinders occurred by gross slip along the {100} planes of the void array – coinciding with the slip planes for the simple cubic system.The mechanical properties of a cellular material comprising a simple cubic array of interconnected spherical voids show cubic elastic symmetry and therefore depend not only on the overall void content but also on the orientation of the applied load to the void array. Qualitatively, the mechanical response can be understood in terms of the {100} slip planes which have low shear strength and stiffness and provide a preferential failure plane as shown in the figure.
      PubDate: 2017-04-07T03:42:20.307864-05:
      DOI: 10.1002/adem.201700060
       
  • Infiltration of Cellular Silicon by Molten Magnesium Alloys 
    • Authors: Alexander Martin Matz; Bettina Stefanie Mocker, Johann Heimann, Norbert Jost
      Abstract: Open-pore cellular Si structures are manufactured by investment casting and, subsequently, infiltrated with molten Mg(-Sn), representing the initial state for a formation of the intermetallic compound Mg2Si1–xSnx. The processing parameters which govern the evolution of microstructure after the infiltration process are studied in the alloy systems Mg-Si and Mg-Si-Sn. The resulting microstructures are analyzed using SEM and EDS. It is found that an initial diffusion layer is already formed after infiltration. Its thickness can slightly be increased by raising the infiltration temperature of the Mg(-Sn) melt. A variation in mold temperature does not show a noticeable impact. The comparison of the diffusion layer formed in the systems Mg-Si and Mg-Si-Sn showed that a lower Sn content resulted in thicker layers.In this study, intermetallic compounds on the example of Mg2Si1–xSnx are fabricated by investment casting of open-pore cellular Si structures and by, subsequently, infiltrating it with molten Mg alloys. The influence of processing parameters and of Sn content on the microstructural evolution is investigated and the initial state for a formation of the intermetallic compound is quantified by respect of the diffusion layer.
      PubDate: 2017-03-23T05:00:30.593537-05:
      DOI: 10.1002/adem.201700023
       
 
 
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